BIOLOGY 

LIBRARY 

G 


-ELEMENTARY    ZOOLOGY 


BY 


VERNON    L.    KELLOGG,    M.S. 

Professor  of  Entomology,  Leland  Stanford  Junior  University 


SECOND  EDITION,  REVISED 


'       -    •    - 

*  .'  •>  •    •  _ 


NEW   YORK 

HENRY    HOLT   AND   COMPANY 
1902 


BIOLOGY 
LIBRARY 


Copyright,  1901, 

BY 

HENRY   HOLT  &  CO. 


ROBERT   DHUMMOND,    PRINTED    NEW  YORK 


PREFACE 

IT  seems  to  the  author  that  three  kinds  of  work  should 
be  included  in  the  elementary  study  of  zoology.  These 
three  kinds  are:  (a)  observations  in  the  field  covering 
the  habits  and  behavior  of  animals  and  their  relations 
to  their  physical  surroundings,  to  plants,  and  to  each 
other  ;  (£)  work  in  the  laboratory,  consisting  of  the  study 
of  animal  structure  by  dissection  and  the  observation  of 
live  specimens  in  cages  and  aquaria ;  and  (c)  work  in  the 
recitation-  or  lecture-room,  where  the  significance  and 
general  application  of  the  observed  facts  are  considered 
and  some  of  the  elementary  facts  relating  to  the  classifi- 
cation and  distribution  of  animals  are  learned. 

These  three  kinds  of  work  are  represented  in  the  course 
of  study  outlined  in  this  book.  The  sequence  and  extent 
of  the  study  in  laboratory  and  recitation-room  are  defi- 
nitely set  forth,  but  the  references  to  field-work  consist 
chiefly  of  suggestions  to  teacher  and  student  regarding 
the  character  of  the  work  and  the  opportunities  for  it. 
Not  because  the  author  would  give  to  the  field-work  the 
least  important  place,  — he  would  not, — but  because  of  the 
utter  impracticability  of  attempting  to  direct  the  field- 
work  of  students  scattered  widely  over  the  United  States. 
The  differences  in  season  and  natural  conditions  in  vari- 
ous parts  of  the  country  with  the  corresponding  differences 
in  the  * '  seasons  ' '  and  course  of  the  life-history  of  the 

221739  '« 


iv  PREFACE 

animals  of  the  various  regions  make  it  impossible  to  in- 
clude in  a  book  intended  for  general  use  specific  direc- 
tions for  field-work.  Further,  the  amount  of  time  for 
field-work  at  the  disposal  of  teacher  and  class  and  the 
opportunities  afforded  by  the  topographic  character  of  the 
region  in  which  the  schools  are  located  vary  much.  The 
initiation  and  direction  of  this  must  therefore  always  de- 
pend on  the  teacher.  On  the  other  hand,  the  work  of  the 
other  two  phases  of  study  can  to  a  large  extent  be  made 
pretty  uniform  throughout  the  country.  For  dissection, 
specimens  properly  killed  and  preserved  are  about  as 
good  as  fresh  material,  and  by  modifying  the  suggested 
sequence  of  work  a  little  to  suit  special  conditions  or  con- 
veniences, the  examination  of  live  specimens  in  the 
laboratory  can  in  most  cases  be  accomplished. 

The  author  believes  that  elementary  zoological  study 
should  not  be  limited  to  the  examination  of  the  struc- 
ture of  several  types.  The  student  should  learn  by 
observation  something  of  the  functions  of  animals  and 
something  of  their  life-history  and  habits,  and  should  be 
given  a  glimpse  of  the  significance  of  his  particular  ob- 
servations and  of  their  general  relation  to  animal  life  as  a 
whole.  The  drill  of  the  laboratory  is  perhaps  the  most 
valuable  part  of  the  work,  but  as  a  matter  of  fact  the  high 
school  is  trying  to  teach  elementary  zoology,  an  ele- 
mentary knowledge  of  animals  and  their  life,  and  dissec- 
tion alone  cannot  give  the  pupil  this  knowledge.  On  the 
other  hand,  without  a  personal  acquaintance  with  animals, 
based  on  careful  actual  observations  of  their  life-history 
and  habits  and  on  the  study  of  the  structural  characters  of 
the  animal  body  by  personally  made  dissections,  the 
pupil  can  never  really  appreciate  and  understand  the  life 
of  animals.  Reading  and  recitation  alone  can  never 
give  the  student  any  real  knowledge  of  it. 

The  book  is  divided  into  three  parts,  of  which  Part  I 


PREFACE  V 

should  be  *  first  undertaken.  This  is  an  introduction  to 
an  elementary  knowledge  of  animal  structure,  function, 
and  development.  It  consists  of  practical  exercises  in 
the  laboratory,  each  followed  by  a  recitation  in  which  the 
significance  of  the  facts  already  observed  is  pointed  out. 
The  general  principles  of  zoology  are  thus  defined  on  a 
basis  of  observed  facts. 

Part  II  is  devoted  to  a  consideration  of  the  principal 
branches  of  the  animal  kingdom ;  it  deals  with  t  system- 
atic zoology.  In  each  branch  one  or  more  examples 
are  chosen  to  serve  as  types.  The  most  important  struc- 
tural features  of  these  examples  are  studied,  by  dissection, 
in  the  laboratory.  The  directions  for  these  dissections 
consist  of  technical  instructions  for  dissecting,  the  calling 
attention  to  and  naming  of  principal  parts,  together  with 
questions  and  demands  intended  to  call  for  independent 
work  on  the  part  of  the  student.  The  directions  follow 
the  actual  course  of  the  dissection  instead  of  being  ar- 
ranged according  to  systems  of  organs,  and  are  intended 
for  the  orientation  of  the  student  and  not  to  be  in  them- 
selves expositions  of  the  anatomy  of  the  types.  The 
condensation  of  these  directions  is  made  more  feasible  by 
the  presence  of  anatomical  plates  (drawn  directly  from 
dissections).  Following  the  account  of  the  dissection  of 
the  type  are  brief  notes  on  its  life-history  and  habits. 

*  This  is  true  if  a  strictly  logical  treatment  of  the  subject  is  held  to.  As 
a  matter  of  fact,  it  is  often  of  advantage  to  begin  with,  or  at  least  to  take  vip 
from  the  beginning  in  connection  with  the  indoor  work,  some  field-work, 
such  as  the  collecting  and  classifying  of  insects  and  the  observation  of 
their  metamorphosis.  As  most  schools  begin  work  in  the  fall,  advantage 
must  be  taken  of  the  favorable  opportunities  for  field-work  at  the  beginning 
of  the  year.  These  opportunities  are  of  course  much  less  favorable  in  the 
winter. 

f  The  classification  of  animals  used  in  this  book  is  that  adopted  in 
Parker  and  Haswell's  "  Text-book  of  Zoology  "  (2  vols.,  1897,  Macmillan 
Co.).  Exception  is  made  in  the  case  of  the  worms,  which  are  considered 
as  a  single  branch,  Vermes,  instead  of  as  several  distinct  branches. 


vi  PREFACE 

Then  follows  a  general  account  of  the  branch  to  which 
the  example  dissected  belongs  and  brief  accounts  of 
some  of  the  more  interesting  members  of  the  branch.  In 
these  accounts  technical  directions  are  given  for  brief 
comparative  examinations  and  for  the  study  of  the  life- 
history  and  habits  of  some  of  the  more  accessible  of 
these  forms. 

It  will  not  be  possible,  of  course,  to  undertake  with  any 
thoroughness  the  consideration  of  all  of  the  branches  of 
animals  in  a  single  year.  But  all  are  treated  in  the  book, 
so  that  the  choice  of  those  to  be  studied  may  rest  with  the 
teacher.  This  choice  will  of  necessity  depend  largely  on 
the  opportunities  afforded  by  the  situation  of  the  school, 
as,  for  example,  whether  on  the  seashore  or  in  the  interior 
near  a  lake  or  river,  or  on  the  dry  plains,  and  on  the  re- 
lation of  the  school-terms  to  the  seasons  of  the  year. 
The  branches  are  arranged  in  the  book  so  that  the  sim- 
plest animals  are  first  considered,  the  slightly  complex 
ones  next,  and  lastly  the  most  highly  organized  forms. 
But  if  in  order  to  obtain  examples  for  study  it  is  necessary 
to  take  up  branches  irregularly,  that  need  not  prove  con- 
fusing. The  author  would  suggest  that  whatever  other 
branches  are  studied,  the  insects  and  birds,  which  are 
readily  available  in  all  parts  of  the  country,  be  certainly 
selected,  and  with  this  selection  in  view  has  given  them 
special  attention.  Indeed  some  teachers  may  find  these 
two  branches  to  offer  quite  sufficient  work  in  classificatory 
and  ecological  lines. 

Part  III  is  devoted  to  a  necessarily  brief  consideration 
of  certain  of  the  more  conspicuous  and  interesting 
features  of  animal  ecology.  It  has  in  it  the  suggestion 
for  much  interesting  field-work.  The  work  of  this  part 
should  be  taken  up  in  connection  with  that  of  Part  II,  as, 
for  example,  the  consideration  of  social  and  communal 
life  in  connection  with  the  insects,  parasitism  in  connec- 


PREFACE  vii 

tion  with  the  worms,  and  also  with  the  insects,  distribu- 
tion in  connection  with  the  birds,  perhaps,  and  so  on. 

In  appendices  there  are  added  some  suggestions  for 
the  outfitting  of  the  laboratory,  and  a  list  of  the  equip- 
ment each  student  should  have.  Here,  also,  is  appended 
a  list  of  a  few  good  authoritative  reference  books  which 
should  be  accessible  to  students  and  to  which  specific 
references  are  made  in  the  course  of  this  book.  Some 
practical  directions  for  the  collecting  and  preserving  of 
specimens  are  also  given.  (Suggestions  for  the  obtaining 
of  material  for  the  various  laboratory  exercises  outlined 
in  the  book  are  to  be  found  in  "technical  notes  "  in- 
cluded in  the  directions  for  each  exercise.)  The  author 
believes  that  the  building  up  of  a  single  school-collection 
in  which  all  the  pupils  have  a  common  interest  and  to 
which  all  contribute  is  to  be  encouraged  rather  than  the 
making  of  separate  collections  by  the  pupils.  Waste  of 
life  is  checked  by  this,  and  in  time,  with  the  contributions 
of  succeeding  classes,  a  really  good  and  effective  collec- 
tion may  be  built  up.  The  ' '  collecting  interest ' '  can 
be  taken  advantage  of  just  as  well  in  connection  with  a 
school-collection  as  with  individual  collections. 

The  plates  illustrating  the  dissections  have  all  been 
drawn  originally  for  the  book  from  actual  dissections. 
Most  of  the  other  figures  are  original,  either  drawn  or 
photographed  directly  from  nature,  or  from  preserved 
specimens.  Credit  is  given  in  each  case  for  figures  not 
original.  The  drawings  for  all  of  the  figures  of  dis- 
sections and  for  all  original  figures  not  otherwise  accred- 
ited were  made  by  Miss  Mary  H.  Wellman,  to  whom  the 
author  expresses  his  obligations.  The  thanks  of  the 
author  are  due  to  Mr.  George  Otis  Mitchell,  San  Fran- 
cisco, who  kindly  made  the  photo-micrographs  of  insect 
structure  from  the  author's  slides;  to  Professor  Mark  V. 
Slingerland,  Cornell  University,  for  electros  of  his  photo- 


viii  PREFACE 

graphs  of  insects;  to  Dr.  L.  O.  Howard,  U.  S.  Entomol- 
ogist, for  electros  of  figs.  45,  52,  56,  68,  81,  82,  83, 
84,  87,  90,  and  92  ;  to  Professor  L.  L.  Dyche,  University 
of  Kansas,  for  photographs  of  his  mounted  groups  of 
mammals;  to  Mrs.  Elizabeth  Grinnell,  Pasadena,  Calif., 
for  photographs  of  birds;  to  Mr.  J.  O.  Snyder,  Stanford 
University,  for  photographs  of  snakes;  to  Mr.  Frank 
Chapman,  editor  of  "  Bird-lore,"  for  electros  of  photo- 
graphs of  birds;  to  Mr.  G.  O.  Shields,  editor  of  "  Recrea- 
tion," for  an  electro  of  the  photograph  of  a  bird;  to  the 
American  Society  of  Civil  Engineers  for  electros  of  photo- 
graphs of  boring  marine  worms;  to  Cassell  &  Co.,  for 
electros  of  three  photographs  from  nature;  to  Geo.  A. 
Clark,  secretary  Fur  Seal  Commission  for  photographs  of 
seals;  and  to  the  Whitaker  and  Ray  Co.,  San  Francisco, 
for  electros  of  figs.  46,  59,  60,  61,  64,  65,  93,  94,  97,  98, 
99,  100,  1 02,  119,  and  166  to  172,  published  originally  in 
Jenkins  &  Kellogg's  "  Lessons  in  Nature  Study."  The 
origin  of  each  of  these  pictures  is  specifically  indicated  in 
connection  with  its  use  in  the  book. 

The  author's  sincere  thanks  are  also  due  to  Mrs.  David 
Starr  Jordan  and  to  Mr.  J.  C.  Brown,  graduate  student  in 
zoology  in  Stanford  University,  for  their  assistance  in  the 
correction  of  the  MS.,  and  in  the  preparation  of  the  lab- 
oratory exercises  respectively.  The  chapters  of  Part  II 
relating  to  the  vertebrates  were  read  in  MS.  by  President 
David  Starr  Jordan,  whose  aid  and  courtesy  are  gratefully 
acknowledged.  Similar  acknowledgments  are  due  Pro- 
fessors Harold  Heath  and  R.  E.  Snodgrass  for  read- 
ing the  proofs  of  the  directions  for  the  laboratory  ex- 
ercises. 

VERNON  LYMAN  KELLOGG. 

STANFORD  UNIVERSITY,  May,  1901. 


CONTENTS 


PART  I 

STRUCTURE,  FUNCTIONS,  AND  DEVELOPMENT  OF 

ANIMALS 

I.— THE  STUDY  OF  ANIMALS  AND  THEIR  LIFE. 

Our  familiar  knowledge  of  animals  and  their  life,  I. — Zoology  and  its 
divisions,  2. — A  first  course  in  Zoology,  3. 

II.— THE  GARDEN  TOAD  (Buro  LEXTIGINOSUS). 
[Laboratory  exercise],  5. — External  structure,  5. — Internal  structure.  7. 

III.— THE  STRUCTURE  AND  FUNCTIONS  OF  THE  ANIMAL  BODY. 

Organs  and  functions,  14. — The  animal  body  a  machine,  14. — The  essen- 
tial functions  or  life-processes,  15. 

IV.— THE  CRAYFISH  (CAMBARUS  SP.). 
[Laboratory  exercise],  17. — External  structure,  17. — Internal  structure,  21. 

V.— THE  MODIFICATION  OF  ORGANS  AND  FUNCTIONS. 

Difference  between  crayfish  and  toad,  26.— Ref-emblances  between  cray- 
ri-li  and  toad,  27. — Modification  of  functions  and  structure  to  fit  the  animal 
to  the  special  conditions  of  its  life,  29.  —Vertebrate  and  invertebrate,  30. 

VI.— AMCEBA  AND  PARAMCLCIUM. 

[Laboratory  exercise],  31. — Amoeba,  31. — The  slipper-animalcule  (PARA- 
MCECIUM  SP.),  34. 

ix 


X  CONTENTS 

VII.— THE  SINGLE-CELLED  ANIMAL  BODY;  PROTOPLASM 

AND  THE  CELL. 
The  single-celled  animal  body,  36. — The  cell,  37.— Protoplasm,  39. 

VIII. -CELLULAR  STRUCTURE  OF  THE  TOAD  (OR  FROG). 
[Laboratory  exercise],  40. — The  blood,   40. — The  skin,   40. — The  liver. 
41. — The  muscles,  41. 

IX.— THE  MANY-CELLED  ANIMAL  BODY;  DIFFERENTIATION 

OF  THE  CELL. 
The  many-celled  animal  body,  43. — Differentiation  of  the  cell,  43. 

X.— HYDRA. 
[Laboratory  exercise],  46. 

XL— THE  SIMPLEST  MANY-CELLED  ANIMALS. 

Cell-differentiation   and   body-organization    in   Hydra,    52.  —  Degrees    in 
cell-differentiation  and  body-organization,  54. 

XII.— DEVELOPMENT  OF  THE  TOAD. 
[Field  and  laboratory  exercise],  55. 

XIII.— MULTIPLICATION  AND  DEVELOPMENT. 

Multiplication,    57  — Spontaneous   generation,   58.  —  Simplest    multiplica- 
tion and  development,  59. — Birth  and  hatching,  61. — Life-history,  62. 


PART  II 

SYSTEMATIC  ZOOLOGY 

XIV.— THE  CLASSIFICATION  OF  ANIMALS. 

[Laboratory  exercise  and  recitation],  65. — Basis  and  significance  01 
classification,  65. — Importance  of  development  in  determining  classification, 
67. — Scientific  names,  68. — An  example  of  classification,  68.  — Species, 
69. -Genus,  70. — Family,  72.  — Order,  72. — Class  and  branch,  73. 

XV.— BRANCH  PROTOZOA  :    THE  ONE-CELLED  ANIMALS. 
EXAMPLE  :     THE    BELL    ANIMALCULE    (VORTICELLA    SP.)    [Laboratory 
exercise],  75. 

OTHER  PROTOZOA. 

Form  of  body,  78. — Marine  Protozoa,  80. 


CONTENTS  xi 

XVI. -BRANCH  PORIFERA:  THE  SPONGES. 

EXAMPLE  :  THE  FRESH-WATER  SPONGE  (SPONGILLA  SP.)  [Laboratory 
exercise],  84. 

EXAMPLE:  A  CALCAREOUS  OCEAN-SPONGE  (GRANTIA  SP.)  [Laboratory 
exercise],  85. 

EXAMPLE:  A  COMMERCIAL  SPONGE  [Laboratory  exercise],  86. 

OTHER  SPONGES. 

Form  and  size,  87.— Skeleton,  88.— Structure  of  body,  88.— Feeding 
habits,  88. — Development  and  life-history,  89. — The  sponges  of  commerce, 
90. — Classification,  91. 

XVII. -BRANCH  CCELENTERATA:    THE  POLYPS,  SEA- 
ANEMONES,  CORALS,  AND  JELLYFISHES. 

POLYPS,    SEA-ANEMONES,    CORALS,    AND   JELLYFISHES. 

General  form  and  organization  of  body,  93. — Structure,  94. — Skeleton, 
95. — Development  and  life-history,  95. — Classification,  96.  — The  polyps, 
colonial  jellyfishes,  etc.  (Hydrozoa),  97. — The  large  jellyfishes,  etc. 
(Scyphozoa),  101. — The  sea-anemones  and  corals  (Actinozoa),  102. — The 
Ctenophora,  107. 

XVIII.— BRANCH   ECHINODERMATA :    THE  STARFISHES,    SEA- 
URCHINS,  SEA  CUCUMBERS,  ETC. 

EXAMPLE  :  STARFISH  (ASTERIAS  SP.)  [Laboratory  exercise]. — External 
structure.  108.  — Internal  structure,  no. — Life-history  and  habits,  113. 

EXAMPLE  :  SEA-URCHIN  (STRONGYLOCENTRUS  SP.)  [Laboratory  exercise]. 
— External  structure,  113. 

OTHER  STARFISHES,  SEA-URCHINS,  SEA  CUCUMBERS,  ETC. 

Shape  and  organization  of  body,  116. — Structure  and  organs,  117. — De- 
velopment and  life-history.  119. — Classification,  120. — Starfishes  (Asteroi- 
dea),  121. — Brittle  stars  (Ophiuroidea),  122. — Sea-urchins  (Echinoidea). 
123. — Sea-cucumbers  (Holothuroidea),  124. — Feather-stars  (Crinoidea),  125. 


XIX.— BRANCH  VERMES:  THE  WORMS. 

EXAMPLE:  THE  EARTHWORM  ILUMBRICUS  SP.)  [Laboratory  exercise] 

External  structure,  127. — internal  structure,  129. — Life-history  and  habits, 

133 

OTHER  WORMS. 

Classification,  135. — Earthworms  and  leeches  (Oligochaetae  ,  136. — Flat 
worms  (Platyhelminlhes).  137. — Round  worms  (Nemathelminthes),  140. — 
Wheel-animalcules  (Rotifera),  142. 


xi  i  CONTENTS 

XX.—  BRANCH  ARTHROPODA  :    THE  CRUSTACEANS,  CEN- 
TIPEDS,  INSECTS,  AND  SPIDERS. 

CLASS  CRUSTACEA:  CRAYFISHES,  CRABS,  LOBSTERS,  ETC. 

EXAMPLE;  THE  CRAYFISH  (CAMBARUS  SP.).  Structure,  146.—  Life-his- 
tory and  habits,  146. 

OTHER  CRUSTACEANS. 

Body  form  and  structure,  147.  —  Water-fleas  (Cyclops],  148.—  Wood-lice 
(Isopoda),  150.  —  Lobsters,  shrimps,  and  crabs  (Decapoda),  151.  —  Barnacle*, 


XXL—  BRANCH  ARTHROPODA  (CONTINUED). 

CLASS  INSECTA  :  THE  INSECTS. 

EXAMPLE  :  THE  RED-LEGGED  LOCUST  (MELANOPLUS  FEMUR-RUBRUM^ 
[Laboratory  exercise].  External  structure,  157.—  Life-history  and  habits, 
161. 

EXAMPLE:  THE  WATER-  SCAVENGER  BEETLE  (HYEROPHILUS  SP.)  [Labo- 
ratory exercise].  External  structure,  163.  —  Internal  structure,  166.  —  Life- 
history  and  habits,  169. 

EXAMPLE  :  THE  MONARCH  BUTTERFLY  (ANOSIA  PLEXIPPUS)  [Laboratory 
exercise].  External  structure,  171.  —  Life-history  and  habits,  175. 

EXAMPLE  :  LARVA  OF  MONARCH  BUTTERFLY  [Laboratory  exercise]. 
Structure,  177. 

OTHER  INSECTS. 

Body  form  and  structure,  181.  —  Development  and  life-history,  188.  — 
Classification,  191.  —  Locusts,  cockroaches,  crickets,  etc.  (Orthoptera),  192. 
—  The  dragon-flies  and  May-flies  (Odonata  and  Ephemerida),  194.  —  The 
sucking-bugs  (Hemiptera),  197.  —  The  flies  (Diptera),  201.  —  The  butterflies 
and  moths  (Lepidoptera).  205.  —  The  beetles  (Coleoptera),  206.  —  The 
ichneumon  flies,  ants,  wasps,  and  bees  (Hymenoptera),  212. 

CLASS  MYRIAPODA  :  THE  CENTIPEDS  AND  MILLIPEDS. 

CLASS  ARACHNIDA  :  THE  SCORPIONS,  SPIDERS,  MITES,  AND  TICS. 


XXII.— BRANCH  MOLLUSCA :  THE  MOLLUSCS. 

EXAMPLE  :  THE  FRESH-WATER  MUSSEL  (L^Nio  SP.)  [Laboratory  exercise]. 
Structure,  239. — Life-history  and  habits,  243. 

OTHER  MOLLUSCS. 

Body  form  and  structure,  245. — Development,  246. — Classification.  246. 
— Clams,  scallops,  and  oysters  (Pelecypoda),  246. — Snails,  slugs,  nudi- 
branchs,  and  "sea-shells"  (Gastropoda),  252.— Squids,  cuttlefishes,  and 
octopi  (Cephalopoda),  255. 


CONTENTS  xiii 

XXIII.— BKANX  II  CHORDATA:  THE  ASCIDTANS,  VERTE- 
BRATES, ETC. 

Structure  of  the  vertebrates,  259. — Classification  of  the  Chordata,  260. — 
The  ascidians,  261. 

XXIV.— BRANCH  CHORDATA  (CONTINUED). 

CLASS  PISCES  :  THE  FISHES. 

EXAMPLE:  THE  GOLDEN  SUNFISH  EUPOMOTIS  GIBBOSUS)  [Laboratory 
exercise].  External  structure,  263. — Internal  structure.  265. — Life-history 
and  habits,  270. 

OTHER  FISHES. 

Body  form   and    structure,  271. — Development   and   life-history,   276. — 
Classification,  277. — The  lancelets  (Leptocardii),  277. — The  lampreys  and 
hag-fishes  (Cyclostomata),  278. — The  true  fishes  (Pisces),  279. — The  sharks, 
skates,   etc.   (Elasmobranchii),  279. — The  bony  fishes  (Teleostomi),  281.  — . 
Habits  and  adaptations,  285.— Food-fishes  and  fish -hatcheries,  288. 

XXV.— BRANCH  CHORDATA  (CONTINUED). 

CLASS  BATRACHIA  :  THE  BATRACHIANS. 

Body  form  and  organization,  292.— Structure,  293. — Life -history  and 
habits.  295. — Classification,  297.  — Mud-puppies,  salamanders,  etc.  (Uro- 
dela),  297. — Frogs  and  toads  (Anura),  299.— Coecilians  (Gymnophiona), 
302. 

XXVI.— BRANCH  CHORDATA  (CONTINUED). 

CLASS  REPTILIA:  THE  SNAKES,  LIZARDS,  TURTLES.  CROCODILES,  ETC. 

EXAMPLE  :  THE  GARTER  SNAKE  (THAMNOPHIS  SP.)  [Laboratory  exer- 
cise]. Structure,  303. — Life-history  and  habits,  308. 

OTHER  REPTILES. 

Body  form  and  organization,  310.  —  Structure,  311, — Life-history  and 
habits,  312. — Classification,  313. — Tortoises  and  turtles  (Chelonia),  314. — 
Snakes  and  lizards  (Squamata\  317. — Crocodiles  and  alligators  (Croco- 
dilia),  325. 

XXVII.— BRANCH  CHORDATA  (CONTINUED). 

CLASS  AVES  :  THE  BIRDS. 

EXAMPLE  :  THE  ENGLISH  SPARROW  i PASSER  DOMES  ncus)  [Laboratory 
exercise].  External  structure,  327. —  Internal  structure  [Laboratory  exer- 
cise], 329. — Life  history  and  habits,  335. 

OTHER  BIRDS. 

Body  form  and  structure,  336.—  Development  and  life-history,  339. — 
Classification.  340.  — The  ostriches,  cassowaries,  etc.  (Rutitx),  341. — The 


xiv  CONTENTS 

loons,  grebes,  auks,  etc.  (Pygopodes),  343.— The  gulls,  terns,  petrels,  and 
albatrosses  (Longipennes),  345. — The  cormorants,  pelicans,  etc.  (Stegano- 
podes),  346. — The  ducks,  geese,  and  swans  (Anseres),  347. — The  ibises, 
herons,  and  bitterns  (Herodiones).  347. — The  cranes,  rails,  and  coots  (Palu- 
dicolse),  348. — The  snipes,  sand-pipers,  plovers,  etc.  (Limicolse),  349. — 
The  grouse,  quail,  pheasants,  turkeys,  etc.  (Gallinse),  358. — The  doves  and 
pigeons  (Columbse),  351. — The  eagles,  hawks,  owls,  and  vultures  (Raptores), 
351. — The  parrots  (Psittaci),  353. — The  cookoos  and  kingfishers  (Coccyges), 
354. — The  woodpeckers  (Pici),  354. — The  whippoorwills,  chimney-swifts, 
and  humming-birds  (Macrochires),  356. — The  perchers  (Passeres),  357.  — 
Determining  and  studying  the  birds  of  a  locality,  359. — Bills  and  feet,  362. 
—  Flight  and  songs,  364. — Nestling  and  care  of  the  young,  366. — Local  dis- 
tribution and  migration,  367. — Feeding  habits,  economics,  and  protection  of 
birds,  370. 

XXVIII.— BRANCH  CHORDATA  (CONTINUED). 

CLASS  MAMMALIA  :  THE  MAMMALS. 

EXAMPLE  :  THE  MOUSE  (Mus  MUSCULUS)  [Laboratory  exercise].  Struc- 
ture, 373. — Life-history  and  habits,  379. 

OTHER  MAMMALS. 

Body  form  and  structure,  381. — Development  and  life-history,  387. — 
Habits,  instincts,  and  reason,  387. — Classification,  388. — The  opossums 
(Marsupialia),  389. — The  rodents  or  gnawers  (Glires),  390. — The  shrews 
and  moles  (Insectivora),  391. — The  bats  (Chiroptera),  391. — The  dolphins, 
porpoises,  and  whales  (Cete),  393.— The  hoofed  mammals  (Ungulata),  394. 
— The  carnivores  (Ferae),  396. — The  man-like  mammals  (Primates),  398. 


PART  III 

ANIMAL  ECOLOGY 

XXIX.— THE  STRUGGLE  FOR  EXISTENCE,  ADAPTATION, 
AND  SPECIES-FORMING. 

The  multiplication  and  crowding  of  animals,  404. — The  struggle  for 
existence,  406. — Variation  and  natural  selection,  406. —  Adaptation  and 
adjustment  to  surroundings,  407.— Species  forming,  408. — Artificial  selec- 
tion, 409. 

XXX.— SOCIAL   AND   COMMUNAL    LIFE,    COMMENSALISM,    AND 
PARASITISM. 

Social  life  and  gregarkmsness,  410. — Communal  life,  411. — Commen- 
salism  413. — Parasitism,  415. 


CONTENTS  xv 

XXXI.— COLOR  AND  PROTECTIVE  RESEMBLANCES. 

Use  of  color,  424. —General,  variable,  and  special  protective  resemblance, 
426. — Warning  colors,  terrifying  appearances,  and  mimicry,  430. — Alluring 
coloration,  433. 

XXXII.— THE  DISTRIBUTION  OF  ANIMALS. 

Geographical  distribution,  435.— Laws  of  distribution,  437. — Modes  of 
migration  and  distribution,  437. — Barriers  to  distribution,  438. —  Faunae 
and  zoogeographic  areas,  440. — Habitat  and  species,  441. — Species-extin- 
guishing and  species-forming,  442. 


APPENDICES 

EQUIPMENT  AND  METHODS 

APPENDIX  I.— EQUIPMENT  AND  NOTES  OF  PUPILS. 
Equipment  of  pupils,  447. — Laboratory  drawings  and  notes,  447. — Field 
observations  and  notes,  448. 

APPENDIX  II.— LABORATORY  EQUIPMENT  AND  METHODS. 

Equipment  of  laboratory,  450.— Collecting  and  preparing  material  for  use 
in  the  laboratory,  451. — Obtaining  marine  animals,  microscopic  prepara- 
tions, etc.,  453. — Reference-books,  454. 

APPENDIX    III.— REARING    ANIMALS    AND    MAKING    COLLEC- 
TIONS. 

Live  cages  and  aquaria,  457.  — Making  collections,  461. — Collecting  and 
preserving  insects,  463. — Collecting  and  preserving  birds,  466. — Collecting 
and  preserving  mammals,  470. — Collecting  and  preserving  other  animals, 
472. 


PART  I 

STRUCTURE,  FUNCTIONS,  AND  DEVELOP- 
MENT OF  ANIMALS 

CHAPTER    I 
THE   STUDY   OF   ANIMALS   AND    THEIR    LIFE 

Our  familiar  knowledge  of  animals  and  their  life.— 

We  are  familiarly  acquainted  with  dogs  and  cats;  less 
familiarly  probably  with  toads  and  crayfishes,  and  we 
have  little  more  than  a  bare  knowledge  of  the  existence 
of  such  animals  as  seals  and  starfishes  and  reindeer.  But 
what  real  knowledge  of  dogs  and  toads  does  our  familiar 
acquaintanceship  with  them  give  ?  Certain  habits  of  the 
dog  are  known  to  us:  it  eats,  and  eats  certain  kinds  of 
food ;  it  runs  about ;  it  responds  to  our  calls  or  even  to 
the  mere  sight  of  us ;  it  evidently  feels  pain  when  struck, 
and  shows  fear  when  threatened.  Another  class  of 
attributes  of  the  dog  includes  those  things  that  we  know 
of  its  bodily  make-up:  its  possession  of  a  head  with  eyes 
and  ears,  nose  and  mouth ;  its  four  legs  with  toes  and 
claws;  its  covering  of  hair.  We  know,  too,  that  it  was 
born  alive  as  a  very  small  helpless  puppy  which  lived  for 
a  while  on  food  furnished  by  the  mother,  and  that  it  has 
grown  and  developed  from  this  young  state  to  a  fully 
grown,  fully  developed  dog.  We  know  also  that  our 
dog  is  a  certain  kind  cf  dog,  a  spaniel,  perhaps,  while 


2  ELEMENTARY  ZOOLOGY 

our  neighbor's  dog  is  of  another  kind,  a  greyhound,  it 
may  be.  We  know  accordingly  that  there  are  different 
kinds  of  tame  dogs,  and  we  may  know  that  wolves 
are  so  much  like  dogs  that  they  might  indeed  be 
called  wild  dogs,  or  dogs  called  a  kind  of  tame  wolf. 
But  how  little  we  really  know  about  the  dog's  body  and 
its  life  is  apparent  at  a  moment's  thought.  We  see  only 
the  outside  of  the  dog,  but  what  an  intricate  complex  of 
parts  really  composes  this  animal!  We  see  it  eat  and 
breathe  and  run ;  of  what  is  done  with  the  food  and  air 
inside  its  body,  and  of  the  series  of  muscle  contractions 
and  mechanical  processes  which  cause  its  running,  we  have 
but  the  slightest  conception.  We  see  that  the  pup  gets 
larger,  that  is,  grows ;  that  it  changes  gradually  in  appear- 
ance, that  is,  develops ;  but  of  the  real  processes  and 
changes  that  take  place  in  growth  and  development  how 
little  we  know !  We  know  that  there  are  other  kinds  of 
dogs;  that  wolves  and  foxes  are  relatives  of  the  dog;  and 
we  have  heard  that  cats  and  tigers  are  relatives  also, 
although  more  distant  ones.  We  know,  too,  that  all  the 
backboned  animals,  some  of  them  very  unlike  dogs,  are 
believed  to  be  related  to  each  other,  but  of  the  thousands  of 
these  animals  and  of  their  relationships  our  knowledge  is 
scanty.  Finally,  of  the  relations  of  the  dog,  and  of  other 
animals,  to  the  outside  world,  and  of  the  wonderful  man- 
ner in  which  the  dog's  make-up  and  behavior  fit  it  to  live 
in  its  place  in  the  world  under  the  conditions  that  surround 
it,  we  have  probably  least  knowledge  of  all. 

Zoology  and  its  divisions. — What  things  we  do  know 
about  the  dog,  however,  and  about  its  relatives,  and 
what  things  others  know,  can  be  classified  into  several 
groups,  namely,  things  or  facts  about  what  the  dog  does, 
or  its  behavior,  things  about  the  make-up  of  its  body, 
things  about  its  growth  and  development,  things  about 
the  kind  of  dog  it  is  and  thejdnds  of  relatives  it  has,  and 


THE  STUDY  OF  ANIMALS  AND    THEIR  LIFE  3 

things  about  its  relations  to  the  outer  world,  and  its  special 
fitness  for  life. 

All  that  is  known  of  these  different  kinds  of  facts  about 
the  dog  constitutes  our  knowledge  of  the  dog  and  its  life. 
All  that  is  known  by  scientific  men  and  others  of  these 
different  kinds  of  facts  about  all  the  500,000  or  more  kinds 
of  living  animals,  constitutes  our  knowledge  of  animals  and 
is  the  science  zoology  *  Names  have  been  given  to  these 
different  groups  of  facts  about  animals.  The  facts  about 
the  bodily  make-up  or  structure  of  animals  constitute  that 
part  of  zoology  called  animal  anatomy  or  morpJiology;  the 
facts  about  the  things  animals  do,  or  the  functions  of 
animals,  compose  animal  physiology;  the  facts  about  the 
development  of  animals  from  young  to  adult  condition  are 
the  facts  of  animal  development;  the  knowledge  of  the 
different  kinds  of  animals  and  their  relationships  to  each 
other  is  called  systematic  zoology  or  animal  classification; 
and  finally  the  knowledge  of  the  relations  of  animals  to 
their  external  surroundings,  including  the  inorganic  world, 
plants  and  other  animals,  is  called  animal  ecology. 

Any  study  of  animals  and  their  life,  that  is,  of  zoology, 
may  include  all  or  any  of  these  parts  of  zoology.  Most 
zoologists  do,  indeed,  devote  their  principal  attention  to 
some  one  group  of  facts  about  animals  and  are  accordingly 
spoken  of  as  anatomists,  or  physiologists,  systematists, 
and  so  on.  But  such  a  specialization  of  study  should  be 
made  only  after  the  zoologist  has  acquired  a  knowledge 
of  the  principal  or  fundamental  facts  in  all  the  other 
branches  of  zoology. 

A  first  course  in  zoology. — The  first  "  course,"  then, 
in  the  study  of  animals  should  include  the  fundamental 
facts  in  all  these  branches  or  parts  of  zoology.  That  is 
what  the  course  outlined  in  this  book  tries  to  cover. 

*  Zoology  is  formed  from  two  Greek  words:  zoon,  meaning  animal,  and 
logos,  meaning  discourse. 


4  ELEMENTARY  ZOOLOGY 

But  no  text-book  of  zoology  can  really  give  the  student 
the  knowledge  he  seeks.  He  must  find  out  most  of  it  for 
himself;  a  text-book,  based  on  the  experiences  of  others, 
is  chiefly  valuable  for  telling  him  how  to  work  most 
effectively  to  get  this  knowledge  for  himself.  And  the 
best  students  always  find  out  things  which  are  not  in  books. 
Especially  can  the  beginning  student  find  out  things  not 
known  before,  * '  new  to  science,  "as  we  say,  about  the 
behavior  and  habits  of  animals,  and  their  relations  to  their 
surroundings.  The  life-history  of  comparatively  few  kinds 
of  animals  is  exactly  known;  the  instincts  and  habits  of 
comparatively  few  have  been  studied  in  any  detail.  The 
kinds  of  food  demanded,  the  feeding  habits,  nest-building, 
care  of  the  young,  cunning  concealment  of  nest  and  self, 
time  of  egg-laying  or  of  producing  young,  duration  of  the 
immature  stages  and  the  habits  and  behavior  of  the  young 
animals — a  host,  indeed,  of  observations  on  the  actual  life 
of  animals,  remain  to  be  made  by  the  "field  naturalist." 
Any  beginning  student  can  be  a  "field  naturalist"  and 
can  find  out  new  things  about  animals,  that  is,  can  add 
to  the  science  of  zoology. 


\ 


CHAPTER    II 
THE     GARDEN     TOAD    (Bufo  lentiginosus) 

LABORATORY  EXERCISE 

TECHNICAL  NOTE. — Although  this  description  is  written  for  the 
toad  it  will  fit  for  the  dissection  of  the  frog.  It  will  be  found,  after 
casting  aside  a  few  ungrounded  prejudices,  that  the  toad  is  the 
better  for  class  dissection.  Toads  are  best  collected  about  dusk, 
when  they  can  be  picked  up  in  almost  any  garden  in  town  or  in  the 
country.  During  the  spring  many  can  be  found  in  the  ponds  where 
they  are  breeding.  To  kill  the  toad  place  it  in  an  air-tight  vessel 
with  a  piece  of  cotton  or  cloth  saturated  in  chloroform  or  ether. 
When  the  toad  is  dead,  wash  off  the  specimen  and  put  in  a  dissect- 
ing pan  for  study.  Several  specimens  should  be  placed  in  a  nitric 
acid  solution  for  a  day  or  so  (for  directions  for  preparing,  see 
p.  12)  to  be  used  later  for  the  study  of  the  nervous  system.  Also 
several  specimens  should  be  injected  for  the  better  study  of  the 
circulatory  system.  With  an  injecting  mass  made  as  directed  on 
p.  451  introduce  through  a  small  canula  into  the  ventricle  of  the 
heart.  This  will  inject  the  arterial  system,  and  with  increased 
pressure  the  injecting  mass  may  be  forced  through  the  valves  of  the 
heart,  thus  passing  into  the  auricles  and  throughout  the  venous 
system.  After  injecting  use  the  specimen  fresh  or  after  it  has  been 
preserved  in  4^  formalin. 

External  structure.  —  Note  that  the  body  of  the  toad 
is  divided  into  several  principal  regions  or  parts,  as  is  the 
human  body,  namely,  a  head,  upper  limbs,  trunk,  and 
lower  limbs.  As  you  look  at  the  toad  note  the  similarity 
of  the  parts  on  one  side  to  those  of  the  other,  as  right  leg 
corresponding  to  left  leg,  right  eye  to  left  eye,  etc.  This 
arrangement  of  the  body  in  similar  halves  among  animals 
is  known  as  bilateral  symmetry.  As  a  rule  animals  which 
show  bilateral  symmetry  move  in  a  definite  direction. 
The  part  that  moves  forward  is  the  anterior  end,  while 

5 


6  ELEMENTARY  ZOOLOGY 

the  opposite  extremity  is  the  posterior  end.  In  most 
animals  we  note  two  other  views  or  aspects ;  that  which 
is  called  the  "back"  and  with  most  animals  is,  under 
ordinary  conditions,  uppermost  is  the  dor  sum  or  dorsal 
aspect,  while  that  which  lies  below  is  the  venter  or  ventral 
aspect.  When  referring  to  a  view  from  one  side  we  speak 
of  it  as  a  right  or  left  lateral  aspect.  These  terms  hold 
good  for  most  of  the  animals  that  we  shall  study. 

Note  at  the  anterior  end  of  the  toad  a  wide  transverse 
slit,  the  mouth.  What  other  openings  are  on  the  anterior 
end  ?  Note  the  two  large  eyes,  the  organs  of  sight.  Just 
back  of  each  eye  note  an  elliptical,  smooth  membrane. 
This  is  the  tympanum  of  the  outer  ear,  and  through  this 
membrane  the  vibrations  produced  by  sound-waves  are 
transferred  to  the  inner  ear,  which  receives  sensations  and 
transmits  them  to  the  brain.  Open  the  mouth  by  drawing 
down  the  lower  jaw.  Note  just  within  the  angle  of  the 
lower  jaw  the  tongue.  How  is  it  attached  to  the  wall  of 
the  mouth  ?  On  the  tongue  are  a  great  many  fine  papilla 
in  which  is  located  the  sense  of  taste.  It  has  now  been 
seen  that  most  of  the  special  senses  of  the  toad  have  their 
seat  in  the  head.  Pass  a  straw  or  bristle  into  one  of  the 
nostrils.  Where  does  it  come  out  ?  These  internal 
openings  to  the  nose  are  the  inner  nares.  Note  in  the 
roof  of  the  mouth  just  posterior  to  each  of  the  eyeballs  an 
opening.  These  are  the  internal  openings  to  the  wide 
Eustachian  tubes,  which  lead  to  the  mouth  from  the 
chamber  of  the  ear  behind  the  tympanum. 

Note  far  back  in  the  mouth  an  opening  through  which 
food  passes.  This  is  the  oesophagus  or  gullet.  Note  just 
below  this  gullet  an  elevation  in  which  is  a  perpendicular 
slit,  the  glottis.  This  is  the  upper  end  of  the  laryngo- 
tracheal  chamber,  and  the  flaps  within  on  either  side  of 
the  slit  are  the  vocal  cords. 

Note  at  the  posterior  end  of  the  body  in  the  median 


THE  GARDEN   TOAD  7 

line  an  opening.  This  is  the  anal  opening  or  amis.  Note 
the  general  make-up  of  the  toad.  How  do  its  arms  com- 
pare with  our  own  ?  How  do  its  fore  feet  (hands)  differ 
from  its  hind  feet  ?  Note  that  the  body  is  covered  by  a 
tough  enveloping  membrane,  the  skin.  In  the  skin  are 
many  glands  which  by  their  excretion  keep  it  soft  and 
moist. 

Internal  structure — TECHNICAL  NOTE.— With  a  fine  pair  of 
scissors  make  a  longitudinal  median  cut  through  the  skin  of  the 
venter  from  the  anal  opening  to  the  angle  of  the  lower  jaw.  Spread 
the  cut  edges  apart  and  pin  back  in  the  dissecting-pan. 

Note  the  complex  system  of  muscles  which  govern  the 
movements  of  the  tongue.  Observe  a  number  of  pairs  of 
muscles  overlying  the  bones  which  support  the  arms. 
These  are  attached  to  the  pectoral  or  shoulder -girdle. 
Note  the  large  sheet  of  muscles  covering  the  ventral 
aspect  of  the  toad.  These  are  the  abdominal  muscle 's, 
which  consist  of  two  sets,  an  outer  and  an  inner  layer. 
Note  that  posteriorly  the  abdominal  muscles  are  attached 
to  a  bone.  This  is  the  pubic  bone  of  the  pelvic  girdle 
which  supports  the  hind  legs. 

TECHNICAL  NOTE. — With  the  scissors  cut  through  the  muscles  of 
the  body  wall  at  the  pubic  bone  and  pass  the  points  forward  to  the 
shoulder-girdle.  Separate  the  bones  of  the  shoulder-girdle  and  pin 
out  the  flaps  of  skin  and  muscle  to  right  and  left  in  the  dissecting- 
pan  (see  fig.  i).  Cover  the  dissection  with  clear  water  or  weak 
alcohol. 

Note  two  large  conspicuous  soft  brown  lobes  of  tissue. 
These  form  the  liver,  an  organ  which  produces  a  secretion 
that  assists  in  the  process  of  digestion.  Note  just  anterior 
to  the  liver  and  extending  between  its  two  lobes  a  pear 
shaped  organ,  the  heart,  which  may  yet  be  pulsating. 
Are  these  pulsations  regular  ?  How  many  occur  in  a 
minute  ?  The  lower  end  or  apex  of  the  heart,  ventricle, 
undergoes  a  contraction,  forcing  blood  out  into  the  blood- 


8  ELEMENTARY  ZOOLOGY 

vessels.  This  is  followed  by  a  relaxation  of  the  apex  and 
a  contraction  of  the  basal  portion,  the  auricle.  'The  heart 
is  surrounded  by  a  delicate  semi-transparent  sac,  the 
pericardium.  The'  pericardium  is  filled  with  a  watery 
fluid,  body-lymph,  which  bathes  the  heart.  Note  between 
the  lobes  of  the  liver  a  small  bladder-shaped  transparent 
organ  of  a  pinkish  color.  This  is  the  gall-cyst,  or  gall- 
bladder, a  reservoir  for  the  bile,  the  secretion  from  the 
liver.  Separate  the  lobes  of  the  liver  and  note,  beneath, 
the  long  convoluted  tube  which  fills  most  of  the  body- 
cavity.  This  is  part  of  the  alimentary  canal.  Is  the 
alimentary  canal  of  uniform  character  ?  The  most  anterior 
portion  of  the  canal,  the  gullet  or  cesopJiagus,  leads  to  a 
large  U-shaped  enlargement,  the  stomach.  From  the  lower 
end  of  the  stomach  there  extends  a  long,  slender,  very 
much  convoluted  tube,  the  small  intestine,  which  is  fol- 
lowed by  a  much  larger  one,  the  large  intestine.  This  large 
intestine  after  one  or  two  turns  passes  directly  back  into 
the  rectum,  which  opens  at  last  to  the  exterior  through  the 
anus.  Note  just  ventral  to  the  rectum  a  large  thin-walled 
membranous  sac.  This  is  the  urinary  bladder  which  acts 
as  a  reservoir  for  the  secretion  from  the  kidneys.  Notice 
a  many-branched  yellow  structure  with  a  glistening 
appearance,  the  fat-body  (corpus  adiposuui).  Now  push 
liver  and  intestine  to  one  side  and  note  the  pinkish  sac-like 
bodies  (perhaps  filled  with  air),  the  lungs.  The  lungs  are 
paired  bodies  which  open  into  the  laryngo-tracheal  cham- 
ber. The  toad  takes  air  into  its  mouth  through  its 
nostrils,  and  then  forces  it,  by  a  kind  of  swallowing  action, 
through  the  laryngo-tracheal  chamber  into  the  lungs. 

Now  lift  the  stomach  and  note  in  the  loop  between  its 
lower  end  and  the  small  intestine  a  thin  transparent  tissue. 
This  is  a  part  of  the  mesentery,  which  will  be  found  to 
suspend  the  whole  alimentary  canal  and  its  attached 
organs  to  the  dorsal  wall  of  the  body.  Note  in  the  loop 


THE  GARDEN   TOAD  9 

of  the  stomach  in  the  mesentery  an  irregular  pinkish 
glandular  structure  which  leads  by  a  small  duct  into  the 
intestine.  This  gland  is  the  pancreas,  and  the  duct  is 
the  pancreatic  duct.  From  it  comes  a  secretion  which 
aids  in  the  digestion  of  food.  Near  the  upper  end  of  the 
pancreas  note  a  round  nodular  structure,  generally  dark 
red.  This  is  the  spleen,  a  ductless  gland,  the  use  of 
which  is  not  altogether  known. 

Make  a  drawing  which  will  show  as  many  of  the  organs 
noted  as  possible. 

TECHNICAL  NOTE. — Pass  two  pieces  of  thread  under  the  rectum 
near  the  pubic  bone.  Tie  these  threads  tightly  a  short  distance 
apart  and  then  cut  the  rectum  in  two  between  the  threads.  Now 
carefully  lift  up  the  alimentary  canal  with  attached  organs  (liver, 
etc.),  and  cut  it  off  near  the  region  of  the  heart. 

How  is  the  heart  situated  with  regard  to  the  lungs  ? 
The  heart  consists  of  a  lower  chamber  with  thick  muscular 
walls,  the  tip,  called  the  ventricle,  and  two  upper  thin- 
walled  chambers,  the  right  and  left  auricles.  Can  you 
make  out  these  three  chambers  ?  The  purified  blood  from 
the  lungs  flows  into  the  left  auricle,  while  the  venous 
blood  from  all  over  the  body  laden  with  its  carbon  dioxide 
enters  the  right  auricle.  From  these  two  chambers  the 
blood  enters  the  ventricle.  Here  the  pure  and  impure 
blood  are  mixed.  From  the  ventricle  the  blood  enters  a 
large  muscular  tube  on  the  ventral  side  of  the  heart.  This 
is  the  conus  arteriosus,  which  gives  off  three  branches  on 
each  side ;  the  anterior  ones,  the  carotid  arteries,  supply 
the  head,  the  next  ones,  the  systemic  arteries,  or  aortce, 
carry  blood  to  the  rest  of  the  body,  while  the  posterior 
vessels,  the  pulmonary  arteries,  go  directly  to  the  lungs 
and  there  break  up  into  fine  vessels  (capillaries)  where 
the  carbon  dioxide  is  given  off  and  oxygen  is  taken  from 
the  air.  From  the  lungs  the  blood  returns  through  the 
puhnonary  vein  to  the  left  auricle.  Meanwhile  the  blood 


10  ELEMENTARY  ZOOLOGY 

which  has  passed  through  the  systemic  arteries  and  body 
capillaries  is  collected  again  into  other  vessels  going  back 
to  the  heart;  these  are  the  veins,  which  empty  into  a  large 
thin-walled  reservoir,  the  sinus  venosus,  which  in  turn 
connects  with  the  right  auricle  of  the  heart.  Three  large 
veins  enter  the  sinus  venosus,  namely,  two  pre-caval  veins 
at  the  anterior  end,  and  a  single  post-caval  vein  at  the 
posterior  end.  Trace  out  the  larger  arteries  and  veins 
from  the  heart  to  their  division  into  or  origin  from  the 
smaller  vessels. 

TECHNICAL  NOTE. — Carefully  remove  the  heart  together  with 
the  lungs.  The  lungs  may  be  inflated  by  blowing  into  them  through 
the  laryngo-tracheal  chamber  with  a  quill  and  tying  them  tightly, 
after  which  they  should  be  left  for  several  days  to  dry.  When 
perfectly  dry,  sections  may  be  cut  through  them  in  various  places 
with  a  sharp  knife,  and  by  this  means  a  very  good  idea  of  the 
simple  lung  structure  of  the  lower  backboned  animals  can  be  ob- 
tained. With  a  sharp  knife  cut  the  heart  open,  beginning  at  the 
tip  (ventricle)  and  cutting  up  through  the  conus  arteriosus  and 
the  two  auricles.  Note  the  valves  in  the  heart  which  separate 
the  different  compartments. 

Note  on  either  side  of  the  median  line  in  the  dorsal 
region  a  pair  of  reddish  glandular  bodies  (the  kidneys). 
From  each  kidney  trace  a  tube  (itreter)  posteriorly  toward 
the  region  of  the  anus.  The  kidneys  are  the  principal 
excretory  organs  of  the  body.  The  blood  which  flows 
through  the  delicate  blood-vessels  in  the  kidney  gives  up 
there  much  of  its  waste  products.  These  pass  out  through 
small  tubules  of  the  kidneys  into  the  ureters,  which  carry 
the  wastes  toward  the  anus.  Along  one  side  of  each 
kidney  may  be  seen  a  yellowish  glistening  mass,  the 
adrenal  body. 

In  some  of  the  specimens  studied,  the  body  cavity  may 
be  filled  with  thousands  of  little  black  spherical  bodies. 
These  are  undeveloped  eggs.  They  are  deposited  by  the 
mother  toad  in  the  water  in  long  strings  of  transparent 
jelly,  which  are  usually  wound  around  sticks  or  plant- 


THE   GARDEN   TOAD 


II 


stems  at  the  bottom  of  the  pond  near  the  shore.      From 
these  eggs  the  young  toads  hatch  as  tadpoles  and  in  their 


,  spheno-ethmoid 
maxillary 


tibio-fibula  * 

astragalus 
FlG.   2. — Skeleton  of  the  garden  toad. 

life-history  pass  through    an  interesting  metamorphosis. 
fSee  Chapter  XII.) 


12  ELEMENTARY  ZOOLOGY 

TECHNICAL  NOTE. — The  teacher  should  be  provided  with  several 
well-cleaned  skeletons  of  the  toad  in  order  that  the  bones  may  be 
carefully  studied.  Boil  in  a  soap  solution  a  toad  trom  which  most 
of  the  muscles  and  skin  have  been  removed  (see  p.  452).  Leave  in 
this  solution  until  the  muscles  are  quite  soft  and  then  pick  off  all 
bits  of  muscles  and  tissue  from  the  bones.  If  this  is  carefully  done, 
the  ligaments  which  bind  the  bones  will  be  left  intact  and  the 
skeleton  will  hold  together. 

Note  that  the  skeleton  (fig.  2)  consists  of  a  head  portion 
which  is  composed  of  many  bones  joined  together  to  form 
a  bony  box,  the  skull;  of  a  series  of  small  segments,  the 
vertebrce,  forming  the  vertebral  column,  which  with  the 
skull  forms  the  axial  skeleton;  and  of  the  appcndicidar 
skeleton,  consisting  of  the  bones  of  the  fore  and  hind  limbs. 
Note  that  the  skull  is  composed  of  many  bones  joined 
together,  some  by  sutures,  while  others  are  fused.  Do 
the  limbs  attach  directly  to  the  axial  skeleton  ?  The 
anterior  limbs  (arms)  articulate  with  the  pectoral  or 
shoulder-girdle.  The  arms  will  be  seen  to  be  made  up 
of  a  number  of  bones  placed  end  to  end.  Note  that  the 
uppermost,  the  Jiumerus,  is  attached  to  the  pectoral 
girdle,  while  at  its  lower  end  it  articulates  with  the 
radio-ulna.  At  the  lower  end  of  the  radio-ulna  is  a  small 
series  of  carpal  bones  which  afford  attachments  for  the 
slender  finger-bones,  \\\e  plialanges  or  digit  a  I  bones.  The 
bones  of  the  leg  are  articulated  with  a  closely  fused  set 
of  bones,  the  pelvic  girdle.  The  leg-bones,  proceeding 
from  the  pelvic  girdle,  are  named  femur,  tibio-filnda, 
tar  sal  bones,  and  phalanges  or  digits.  To  what  bones  of 
the  arm  do  these  correspond  ?  Determine  the  other 
principal  bones  of  the  skeleton  by  reference  to  figure  2. 

TECHNICAL  NOTE. — In  a  specimen  which  has  been  macerated 
for  some  time  in  20%  nitric  acid  dissect  out  the  nervous  system. 
Place  the  specimen  in  a  pan  ventral  side  uppermost  and  pin  out. 
Carefully  pick  away  the  vertebrae  and  the  roof  of  the  mouth-cavity, 
thereby  exposing  the  central  nervous  system,  which  will  appear 
light  yellow. 


THE  GARDEN   TOAD  13 

Examine  the  brain.  In  front  of  the  true  brain  are  the 
olfactory  lobes,  the  nervous  centre  for  the  sense  of  smell. 
The  brain  itself  is  composed  of  several  parts.  The 
anterior  portion  consists  of  two  elongated  parts,  the 
cerebral  hemispheres;  just  back  of  these  are  the  optic  lobes 
or  midbrain,  consisting  of  two  short  lobes,  which  are  fol- 
lowed by  the  small  cerebellum,  which  in  turn  is  followed 
by  a  long  part,  the  medulla  oblongata,  which  runs  imper- 
ceptibly into  the  long  dorsal  nerve,  the  spinal  cord.  Note 
the  large  optic  nerves  running  out  to  each  eye.  How  far 
backward  does  the  spinal  cord  extend  ?  Note  the  many 
pairs  of  nerves  given  off  from  the  brain  and  spinal  cord. 
These  nerves  branch  and  subdivide  until  they  end  in  very 
fine  fibres.  Some  end  in  the  muscle-fibres,  and  through 
them  the  central  nervous  system  innervates  the  muscles. 
These  are  motor  endings.  Still  others  pass  to  the  surface 
and  receive  impressions  from  the  outside.  These  last  are 
sensory  endings.  Note  that  the  spinal  nerves  arise  from 
the  spinal  cord  by  two  roots,  an  anterior  or  ventral,  and 
a  posterior  or  dorsal  root.  Trace  the  principal  spinal 
nerves  to  the  body-parts  innervated  by  them.  These 
nerves  are  numbered  as  first,  second,  etc.,  according  to 
the  number  of  the  vertebrae  (counting  from  the  head  back- 
ward) from  behind  which  they  arise. 


CHAPTER   III 

THE    STRUCTURE    AND    FUNCTIONS    OF    THE 
ANIMAL    BODY 

Organs  and  functions. — The  body  of  the  toad  is  com- 
posed of  various  parts,  such  as  the  lungs,  the  heart,  the 
muscles,  the  eyes,  the  stomach,  and  others.  The  life  of 
the  toad  consists  of  the  performance  by  it  of  various 
processes,  such  as  breathing,  digesting  food,  circulating 
blood,  moving,  seeing,  and  others.  These  various 
processes  are  performed  by  the  various  parts  of  the  body. 
The  parts  of  the  body  are  called  organs,  and  the  processes 
(or  work)  they  perform  are  called  their  functions.  The 
lungs  are  the  principal  organs  for  the  function  of  breath- 
ing; the  heart,  arteries  and  veins  are  the  organs  which 
have  for  their  function  the  circulation  of  the  blood ;  the 
principal  organ  concerned  in  the  digestion  of  food  is  the 
alimentary  canal,  the  function  of  seeing  is  performed  by 
the  organs  of  sight,  the  eyes,  and  so  one  might  continue 
the  catalogue  of  all  the  organs  of  the  body  and  of  all  the 
functions  performed  by  the  animal. 

The  animal  body  a  machine. — The  whole  body  of  the 
toad  is  a  machine  composed  of  various  parts,  each  part 
with  its  special  work  or  business  to  do,  but  all  depending 
on  cne  another  and  all  co-operating  to  accomplish  the  total 
work  of  living.  The  locomotive  engine  is  a  machine 
similarly  composed  of  various  parts,  each  part  with  its 
special  work  or  function,  and  all  the  parts  depending  on 
one  another  and  so  working  together  as  to  perform  satis- 

14 


STRUCTURE  AND  FUNCTIONS  OF  THE  ANIMAL  BODY    15 

factorily  the  work  for  which  the  locomotive  engine  is 
intended.  An  important  difference  between  the  locomo- 
tive engine  and  the  toad's  body  is  that  one  is  a  lifeless 
machine  and  the  other  a  living  machine.  But  there  is  a 
real  similarity  between  the  two  in  that  both  are  composed 
of  special  parts,  each  part  performing  a  special  kind  of 
work  or  function,  and  all  the  parts  and  functions  so  fitted 
together  as  to  form  a  complex  machine  which  successfully 
accomplishes  the  work  for  which  it  is  intended.  And  this 
similarity  is  one  which  should  help  make  plain  the  funda- 
mental fact  of  animal  structure  and  physiology,  namely, 
the  division  of  the  body  into  numerous  parts  or  organs, 
and  the  division  of  the  total  work  of  living  into  various 
processes  which  are  the  special  work  or  functions  of  the 
various  organs. 

The  essential  functions  or  life-processes. — The  toad 
has  a  great  many  different  special  parts  in  its  body.  Its 
body  is  very  complex.  It  performs  a  great  many  differ- 
ent functions,  that  is,  does  a  great  many  different  things 
in  its  living.  And  the  structure  and  life  of  most  of  the 
other  animals  with  which  we  are  familiar  are  similarly 
complex:  a  fish,  or  a  rabbit,  or  a  bird  has  a  body  com- 
posed of  many  different  parts,  and  is  capable  of  doing 
many  different  things.  Are  all  animals  similarly  complex 
in  structure,  and  capable  of  doing  such  a  great  variety  of 
things  ?  We  shall  find  that  the  answer  to  this  question 
is  No.  There  are  many  animals  in  which  the  body  is 
composed  of  but  a  few  parts,  and  whose  life  includes  the 
performance  of  fewer  functions  or  processes  than  in  the 
case  of  the  toad.  There  are  many  animals  which  have 
no  eyes  nor  ears  nor  other  organs  of  special  sense. 
There  are  animals  without  legs  or  other  special  organs  of 
locomotion ;  some  animals  have  no  blood  and  hence  no 
heart  nor  arteries  and  veins.  But  in  the  life  of  every 
animal  there  are  certain  processes  which  must  be  per- 


16  ELEMENTARY  ZOOLOGY 

formed,  and  the  body  must  be  so  arranged  or  composed 
as  to  be  capable  of  performing  these  necessary  life- 
processes.  All  animals  take  food,  digest  it,  and  assimi- 
late it,  that  is,  convert  it  into  new  body  substance ;  all 
animals  take  in  oxygen  and  give  off  carbonic  acid  gas; 
all  animals  have  the  power  of  movement  or  motion  (not 
necessarily  locomotion) ;  all  animals  have  the  power  of 
sensation,  that  is,  can  feel;  all  animals  can  reproduce 
themselves,  that  is,  produce  young.  These  are  the 
necessary  life-processes.  It  is  evident  that  the  toad  could 
still  live  if  it  had  no  eyes.  Seeing  is  not  one  of  the 
necessary  functions  or  processes  of  life.  Nor  is  hearing, 
nor  is  leaping,  nor  are  many  of  the  things  which  the  toad 
can  do ;  and  animals  can  exist,  and  do  exist,  without  any 
of  those  organs  which  enable  the  toad  to  see  and  hear  and 
leap.  But  the  body  of  any  animal  must  be  capable  of 
performing  the  few  essential  processes  which  are  necessary 
to  animal  life.  How  surprisingly  simple  such  a  body  can 
be  will  be  later  discovered.  But  in  most  animals  the 
body  is  a  complicated  object,  and  is  able  to  do  many 
things  which  are  accessory  to  the  really  essential  life- 
processes,  and  which  make  its  life  complex  and  elaborate. 


CHAPTER    IV 
THE     CRAYFISH     (Camdarus  sp.) 

LABORATORY   EXERCISE 

TECHNICAL  NOTE. — The  crayfish,  or  crawfish,  is  found  in  most  of 
the  fresh-water  ponds  and  streams  of  the  United  States.  (It  is  not 
found  east  of  the  Hoosatonic  River,  Mass.  In  this  region  the  lob- 
ster may  be  used.  On  the  Pacific  coast  the  crayfishes  belong  to  the 
genus  Astacus.}  Crayfishes  may  be  taken  by  a  net  baited  with  dead 
fish,  or  they  may  be  caught  in  a  trap  made  from  a  box  with  ends 
which  open  in,  and  baited  with  dead  fish  or  animal  refuse  of  any 
sort.  This  box  should  be  placed  in  a  pond  or  stream  frequented 
by  crayfish.  If  possible  the  student  should  study  the  living  animal 
and  observe  its  habits.  Crayfish  which  are  to  be  kept  alive  should  be 
placed  in  a  moist  chamber  in  a  cool  place.  They  will  keep  for  a 
longer  time  in  a  moist  chamber  than  in  water.  Some  fresh  specimens 
should  be  injected  by  the  teacher  for  the  study  of  the  circulatory 
system.  A  watery  solution  of  coloring  matter  or,  better,  of  an  in- 
iecting  mass  of  gelatine  (see  p.  451)  is  injected  into  the  heart 
through  the  needle  of  a  hypodermic  syringe.  For  the  purpose  of 
injecting,  a  small  bit  of  the  shell  may  be  removed  from  the  cephalo- 
thorax  above  the  heart.  Specimens  which  are  to  be  kept  for  some 
time  should  be  placed  in  alcohol  or  4^  formalin. 

External  structure  (fig.  3). — Place  a  specimen  in  a 
pan  for  study.  Note  that  the  body,  which  of  course  differs 
much  in  shape  from  that  of  the  toad,  is  also  unlike  that  of 
the  toad  in  being  covered  by  a  hard  calcareous  cxoskclcton, 
which  acts  as  a  covering  for  the  soft  parts  and  also  as  a 
place  of  attachment  for  the  muscles,  just  as  the  internal 
skeleton  does  in  the  case  of  the  toad.  The  body  is  com- 
posed of  an  anterior  part,  the  cephalotJiorax,  and  a 
posterior  part,  the  abdomen.  The  cephalothorax  is  covered 
above  and  on  the  sides  by  the  carapace,  which  is  divided 
into  parts  corresponding  to  the  head  and  thorax  of  the 

17 


i8 


ELEMENTARY   ZOOLOGY 


antennule 


opening  of  green  gland 


maxillipeds----f- 


thorax 


genital  aperture 


.''  anus 

,.,-"uropod 

—telson 


JTIG.  3. — Ventral  aspect  of  crayfish  (Cambarus  sp.),  with  the  appendages  ot 
one  side  disarticulated. 


THE  CRAYFISH  *9 

toad  by  the  transverse  cervical  suture.  The  abdomen 
is  composed  of  segments.  How  many  ?  The  flattened 
terminal  segment  is  called  the  telson.  Is  the  cephalo- 
thorax  composed  of  segments  ?  Where  is  the  mouth  of 
the  crayfish  ?  Where  is  the  anal  opening  ? 

At  the  anterior  end  of  the  cephalothorax  note  a  sharp 
projection,  the  rostrum.  Where  are  the  eyes  ?  Remove 
one  of  them  and  examine  its  outer  surface  with  a  micro- 
scope. A  bit  of  the  outer  wall  should  be  torn  off  and 
mounted  on  a  glass  slide.  Note  that  it  is  made  up  of  a 
great  many  little  facets  placed  side  by  side.  Each  of 
these  facets  is  the  external  window  of  an  eye  element  or 
ommatidium.  An  eye  composed  in  this  way  is  called  a 
compound  eye.  In  front  of  the  eyes  note  two  pairs  of 
slender  many-segmented  appendages.  The  shorter  pair, 
the  antenmdes,  are  two-branched.  Remove  one  of  them 
and  note  at  its  base  a  small  slit  along  the  upper  surface. 
This  slit  opens  into  a  small  bag-like  structure  which  con- 
tains fine  sand-grains.  The  bag  is  protected  by  a  series 
of  fine  bristles  along  the  edge  of  the  slit.  This  bag-like 
structure  is  believed  to  be  an  auditory  organ.  The  longer 
pair  of  appendages  are  the  antennce,  and  in  the  fine  hair- 
like  projections  upon  the  joints  is  believed  to  be  located 
the  sense  of  smell.  Thus  it  will  be  seen  that  the  sense- 
organs  of  the  crayfish,  like  those  of  the  toad,  are  located 
on  the  head.  Beneath  the  basal  portion  of  each  antenna 
there  is  a  flat  plate-like  projection,  at  the  base  of  which 
on  the  upper  edge  will  be  noted  a  small  opening,  the 
exit  of  the  kidney,  or  green  gland. 

Make  a  drawing  of  the  surface  of  part  of  an  eye ;  also 
of  an  antennule ;  and  of  an  antenna. 

TECHNICAL  NOTE. — Stick  one  point  of  the  scissors  under  the 
posterior  end  of  the  carapace  on  the  right  side,  and  cut  forward, 
thus  exposing  a  large  cavity,  the  gill-chamber.  Remove  all  of  the 
mouth-parts,  legs  and  abdominal  appendages  from  the  right  side, 
being  careful  to  leave  the  fringe-like  parts,  the  gills,  attached  to 


20  ELEMENTARY  ZOOLOGY 

their  respective  legs.     Place  all  of  the  appendages  in  order  on  a 
piece  of  cardboard. 

Examine  the  abdominal  appendages,  called  pleopods, 
or  swimming  feet.  How  many  pairs  are  there  ?  Each 
is  composed  of  a  basal  part,  the  protopodite,  and  two 
terminal  segments,  an  inner  one,  the  endopodite,  and  an 
outer,  the  exopodite.  In  the  males  the  first  and  second 
pleopods  of  the  abdomen  are  larger  and  less  flexible  than 
the  others.  In  the  female  the  pleopods  serve  to  carry 
the  eggs  and  the  first  two  pairs  are  very  small  or  absent. 
Note  the  last  set  of  abdominal  appendages.  These  are 
the  uropods,  which  together  with  the  telson  form  the  tail. 

Make  a  drawing  of  the  pleopods  of  one  side. 

Examine  the  appendages  of  the  cephalothorax.  Like 
the  appendages  of  the  abdomen  the  typical  composition 
of  each  includes  a  protopodite,  an  exopodite  and  an 
endopodite,  but  some  of  these  appendages  are  much 
modified,  and  show  a  loss  of  one  of  these  parts,  or  the 
addition  of  an  extra  part.  The  cephalothoracic  appen- 
dages may  be  divided  into  three  groups,  an  anterior  group 
of  three  pairs  of  mouth-parts  (belonging  to  the  head)  of 
which  the  first  pair  is  the  mandibles  and  the  others  are  the 
maxillcz;  a  second  group  of  three  pairs  of  foot-jaws  or 
maxillipeds,  belonging  to  the  thorax,  and  a  third  group  of 
five  pairs  of  walking- -legs.  The  mandibles,  lying  next  to 
the  mouth-opening,  are  hard  and  jaw-like  and  lack  the 
exopodite ;  the  first  maxillae  are  small  and  also  lack  the 
exopodite;  the  second  maxillae  have  a  large  paddle-like 
structure  which  extends  back  over  the  gills  on  each  side 
within  the  space,  the  branchial  chamber,  above  the  gills. 
It  is  by  means  of  this  paddle-like  structure  (the  scaphog- 
nathite)  that  currents  of  water  are  kept  up  through  the 
gill-chambers.  The  maxillipeds  increase  in  size  from 
first  to  third  pair.  Each  pair  of  walking-legs  except  the 
last  bears  gills.  These  gills  are  the  organs  by  which 


THE  CRAYFISH  21 

the  blood  is  purified.  The  blood  of  the  crayfish  flows  into 
the  large  vessels  on  the  outer  sides  of  the  gill  and  thence 
into  the  fine  vessels  in  the  little  leaf-like  lamellae.  At  the 
same  time  the  air  which  is  mixed  with  the  water  bathing 
the  gills  passes  freely  through  the  thin  membranous  walls 
of  these  lamellae  and  blood-vessels,  and  the  blood  gives 
off  its  carbonic  acid  gas  to  the  water  and  takes  up  oxygen 
from  the  air  in  the  water.  Thus  it  will  be  seen  that  the 
office  of  the  gill  is  like  that  of  the  lung  in  the  toad, 
namely,  to  act  as  an  organ  for  the  elimination  of  carbonic 
acid  gas  and  the  taking  up  of  oxygen. 

Note  the  pincer-like  appendages  of  the  first  pair  of  legs. 
These  pincers  are  the  chclce,  with  which  food  is  torn  into 
bits  and  placed  in  the  mouth.  In  the  basal  segment  of 
each  of  the  last  pair  of  legs  of  the  male  note  the  genital 
pore.  In  the  female  the  genital  pores  are  in  the  basal 
segments  of  the  next  to  last  pair  of  legs.  Is  the  crayfish 
bilaterally  symmetrical  ?  Note  the  repetition  of  parts  in 
the  crayfish,  that  is,  the  recurrence  of  similar  parts  in 
successive  segments.  This  serial  repetition  of  parts  among 
animals  is  called  metemerism. 

Internal  Structure  (fig.  4).— TECHNICAL  NOTE.—  With  a  pair 
of  scissors  cut  through  the  dorsal  wall  of  the  cephalothorax  into  the 
body-cavity.  Cut  the  body-wall  away  from  both  sides  and  remove 
the  middle  portion. 

At  the  anterior  end  of  the  cephalothorax  note  the  large 
membranous  sac,  the  stomach.  Attached  to  each  end  of 
this  are  sets  of  muscles  which  control  its  movements. 
To  the  right  and  left  of  the  stomach  notice  attached  to 
the  shell  large  muscles  which  connect  by  stout  ligaments 
at  their  lower  ends  with  the  mandibles.  Note  a  yellow 
fringe-like  structure,  the  digestive  gland,  which  fills  most 
of  the  region  about  the  stomach.  It  connects  by  a  pair 
of  small  tubes,  the  bile-ducts,  with  the  alimentary  canal. 
Within  the  posterior  portion  of  the  cephalothorax  note  a 


ELEMENTARY  ZOOLOGY 


THE  CRAYFISH  23 

pentagonal  sac,  the  heart,  contained  within  a  delicate 
membrane,  the  pericardium.  Remove  the  pericardium 
and  note  a  pair  of  dorsal  openings  into  the  heart,  called 
ostia.  (There  are  also  two  lateral  pairs  and  a  ventral 
pair  of  ostia.)  Note  passing  anteriorly  from  the  heart 
along  the  median  line  to  the  eyes  a  blood-vessel,  the 
ophthalmic  artery.  Arising  from  the  anterior  portion  of 
the  heart  are  the  antennary  arteries,  running  to  the 
antennae.  Yet  another  pair  running  anteriorly  from  the 
heart  to  the  stomach  and  digestive  glands  are  called  the 
hepatic  arteries.  From  the  posterior  end  of  the  heart 
arises  the  dorsal  abdominal  artery,  running  back  to  the 
telson.  Below  this  arises  the  sternal  artery,  which  will 
be  seen  later. 

In  the  region  below  the  heart  are  located  the  reproduc- 
tive organs.  They  are  whitish  glandular  masses  from 
each  of  which  runs  a  tube  which  opens  at  the  base  of  the 
last  pair  of  walking-legs  in  the  male,  and  at  the  base  of 
the  third  pair  of  walking-legs  in  the  female. 

TECHNICAL  NOTE. — Cut  longitudinally  through  the  dorsal  wall 
of  the  abdomen  on  either  side  of  the  median  line  and  remove  the 
piece  of  shell. 

Note  the  powerful  muscles  within  which  flex  and  extend 
the  abdomen.  By  a  rapid  contraction  of  these  muscles 
the  tail  is  brought  beneath  the  body,  propelling  the  animal 
strongly  backwards.  When  the  crayfish  crawls  it  gen- 
erally goes  forward,  but  in  swimming  it  reverses  this 
direction. 

Make  a  drawing  showing,  in  their  natural  position,  the 
internal  organs  which  have  been  studied. 

Examine  the  alimentary  canal  for  its  whole  length. 
Note  that  the  large  bladder-shaped  stomach  is  attached 
to  the  mouth-opening  by  a  short  tube.  What  part  of  the 
canal  is  this  ?  From  the  posterior  end  of  the  stomach  is 
a  short  thick-walled  part,  the  small  intestine,  followed  by 


24  ELEMENTARY  ZOOLOGY 

a  long  straight  tube,  the  large  intestine,  which  opens  to 
the  exterior  through  the  anus. 

TECHNICAL  NOTE. — Remove  the  alimentary  canal,  detaching  it 
from  the  anal  end  first,  and  working  forward. 

Cut  the  stomach  open.  Note  an  anterior  portion,  the 
cardiac  cJiamber,  and  a  smaller  posterior  portion,  the 
pyloric  chamber.  Examine  its  inner  surface.  What  do 
you  find  here  ?  This  structure  is  called  the  gastric  mill. 
Food,  which  for  the  most  part  consists  of  any  dead 
organic  matter,  is  chewed  by  the  ' '  stomach-teeth  ' '  into 
fine  bits,  and  is  then  passed  into  the  pyloric  chamber.  It 
is  here  that  the  digestive  glands  empty  their  secretion  into 
the  food.  These  glands  have  the  same  office  as  have  the 
liver  and  pancreas  combined  in  the  toad,  and  so  they  are 
often  called  the  hepato-pancreas.  When  the  stomach  has 
been  removed  there  will  be  noted  in  the  anterior  portion 
of  the  body  paired,  flattened  bodies,  already  mentioned, 
which  connect  with  openings  at  the  base  of  each  of  the 
antennae  by  means  of  wide  thin-walled  sacs,  the  ureters. 
These  organs  are  the  kidneys,  or  green  glands.  Their 
office  is  similar  to  that  of  the  kidneys  in  the  toad,  namely, 
the  elimination  of  waste  from  the  body. 

TECHNICAL  NOTE. — Carefully  remove  all  of  the  alimentary  canal, 
digestive  glands,  and  reproductive  organs.  This  process  will  expose 
the  floor  of  the  cephalothorax.  Now  cut  away  from  either  side  the 
horny  floor  or  bridge  at  the  bottom  of  the  cephalothorax.  If  the 
specimen  has  not  already  been  immersed,  place  it  in  clear  water  for 
further  dissection. 

The  foregoing  dissection  will  expose  the  central  nervous 
system.  It  extends  as  a  series  of  paired  ganglia  con- 
nected by  a  double  nerve-cord  along  the  ventral  median 
line  from  the  oesophagus  to  the  last  segment  of  the 
abdomen.  From  what  points  do  the  lateral  nerves  arise  ? 
Anteriorly  the  double  nerve-cord  divides,  the  two  parts 


THE  CRAYFISH  25 

passing  upward  on  each  side  of  the  oesophagus,  where  they 
again  meet  to  form  the  supra-oesopJiageal  ganglion  or 
brain.  Where  do  the  nerves  run  which  rise  from  the 
brain  ?  What  is  the  difference  between  the  position  of 
the  central  nervous  system  in  the  crayfish  and  in  the  toad  ? 

Make  a  drawing  of  the  nervous  system. 

Just  beneath  the  nerve-cord  note  a  blood-vessel  ex- 
tending the  length  of  the  body.  This  is  the  sternal 
artery,  which  arises  from  the  posterior  end  of  the  heart 
and  passes  ventrally  at  one  side  of  the  alimentary  canal 
and  between  the  nerve-cords.  Here  the  sternal  artery 
divides  into  an  anterior  and  a  posterior  branch,  from 
which  lesser  branches  are  given  off  to  each  one  of  the 
appendages.  The  various  arteries  running  to  all  parts  of 
the  body  finally  pour  out  the  blood  into  the  body-cavity, 
where  it  flows  freely  in  the  spaces  among  the  various  tissues 
and  organs.  After  the  blood  has  bathed  the  body  tissues 
it  flows  to  the  gills  on  either  side,  passing  up  the  outer 
side  of  the  gill  through  delicate  thin-walled  vessels,  where 
it  is  oxygenated  as  has  already  been  described.  From 
the  gills  the  purified  blood  flows  back  on  the  inner  side 
through  a  large  chamber,  sinus,  into  the  pericardium, 
through  the  ostia  of  the  heart,  whence  it  is  driven  into  the 
arteries  once  more.  This  sort  of  a  circulatory  system  in 
which  the  blood  in  places  is  not  enclosed  in  a  definite 
vessel  is  known  as  an  open  system.  In  the  toad  we  find 
the  blood  in  a  dosed  system,  i.e.,  arteries  leading  into 
capillaries  which  in  turn  lead  into  veins,  in  no  case  allow- 
ing the  blood  to  pass  freely  through  the  spaces  of  the 
body. 


CHAPTER    V 

THE   MODIFICATION   OF  ORGANS  AND  FUNC- 
TIONS 

Differences  between  crayfish  and  toad. — In  the  dis- 
section of  the  crayfish  one  of  the  most  important  things  in 
the  study  of  zoology  has  been  learned.  It  is  plain  that 
the  crayfish  has  a  body  composed,  like  the  toad's,  of 
parts  or  organs,  and  that  most  of  these  organs,  although 
differing  much  in  appearance  and  actual  structure  from 
those  of  the  toad,  correspond  to  similarly  named  organs 
of  the  toad,  and  perform  the  same  functions  or  processes, 
although  with  many  striking  differences,  essentially  in  the 
same  way  as  in  the  toad.  But  the  structure  of  the  body 
is  very  different  in  the  two  animals.  The  toad  has  an 
internal  body  skeleton  to  which  the  muscles  are  attached, 
and  a  soft,  yielding,  outer  body-covering  or  skin ;  the 
crayfish  has  no  internal  skeleton,  but  has  its  body  covered 
by  a  horny,  firm  body-wall  to  which  the  muscles  are 
attached.  The  toad  has  its  main  nervous  chain  lying  just 
beneath  the  dorsal  wall  of  the  body;  the  crayfish  has  its 
main  nervous  chain  lying  just  above  the  ventral  wall  of 
the  body.  The  toad  has  lungs  and  takes  up  oxygen  from 
the  air  of  the  atmosphere ;  the  crayfish  has  gills  and  takes 
up  oxygen  from  the  air  which  is  mixed  with  the  water. 
The  toad  has  a  single  pair  of  jaws;  the  crayfish  has 
several  pairs  of  mouth-parts.  The  toad  has  four  legs 
fitted  for  leaping;  the  crayfish  has  numerous  legs  fitted 
for  crawling  or  swimming.  The  crayfish's  body  is  com- 

26 


THE  MODIFICATION  OF  ORGANS  AND   FUNCTIONS       27 

posed  of  a  series  of  body-rings  or  segments;  the  toad's 
body  is  a  compact  apparently  unsegmented  mass.  The 
toad  has  eyes  each  with  a  single  large  lens  and  capable 
of  moving  in  the  head  and  of  changing  their  shape  and 
hence  their  focus;  the  crayfish's  eyes  are  immovable  and 
have  a  fixed  focus,  and  are  composed  of  hundreds  of  tiny 
eyes  each  with  lens  and  special  retina  of  its  own.  And 
so  a  long  list  of  differences  might  be  gone  through  with. 

Resemblances  between  toad  and  crayfish. — But  on  the 
other  hand  there  are  many  resemblances — resemblances 
both  in  structure  and  life-processes  or  physiology.  Both 
toad  and  crayfish  have  organs  for  the  prehension  of  food, 
its  digestion  and  its  assimilation.  And  these  organs,  the 
organs  of  the  digestive  system,  while  differing  in  details 
are  alike  in  being  composed  principally  of  a  long  tube, 
the  alimentary  canal,  running  through  the  body,  open 
anteriorly  for  the  taking  in  of  food,  and  open  posteriorly 
for  the  discharge  of  indigestible  useless  matter.  Both 
alimentary  canals  are  divided  into  various  special  regions 
for  the  performance  of  the  various  special  processes  con- 
nected with  the  digestion  and  assimilation  of  food.  Each 
is  adapted  for  the  special  kind  of  food  which  it  is  the  habit 
of  the  particular  animal  to  take.  The  two  sets  of  organs 
are  essentially  alike  and  have  the  same  essential  function 
or  life-process  to  perform.  But  this  process  differs  in  the 
details  of  its  performance,  and  the  organs  which  perform 
this  function  and  which  constitute  the  digestive  system  of 
each  are  modified  to  suit  the  special  habits  or  kind  of  life 
of  the  animal. 

Both  toad  and  crayfish  have  a  heart  w^ith  blood-vessels 
leading  from  it.  In  the  case  of  the  toad  the  heart  is  more 
complex  than  in  the  crayfish,  and  the  system  of  blood- 
vessels is  far  more  extensive  and  elaborate.  But  the  heart 
and  blood-vessels  in  both  animals  subserve  the  same  pur- 
pose; their  function  is  the  circulation  of  the  blood,  this 


28  ELEMENTARY  ZOOLOGY 

being  the  means  by  which  oxygen  and  food  are  carried 
to  all  growing  or  working  parts  of  the  body,  and  by 
which  carbonic  acid  gas  and  other  poisonous  waste 
products  are  brought  away  from  these  parts.  But  this 
function  differs  somewhat  in  its  performance  in  the  two 
animals,  and  the  organs  which  perform  the  function  are 
correspondingly  modified  in  structural  condition. 

Both  toad  and  crayfish  have  organs  for  respiration,  that 
is,  for  breathing  in  oxygen  and  breathing  out  carbonic 
acid  gas.  But  the  toad  takes  its  oxygen  from  the 
atmosphere  about  it;  its  respiratory  organs  are  the 
lungs,  the  sac-like  tube  leading  to  the  mouth,  and 
the  external  openings  for  the  ingress  and  exit  of  the 
gases.  The  crayfish,  living  mostly  in  the  water,  takes 
its  oxygen  from  the  air  which  is  mechanically  mixed 
with  the  water.  Its  respiratory  organs  are  its  gills. 
There  is  a  great  difference,  apparently,  in  the  structural 
.conditions  of  the  organs  of  respiration  in  the  two  animals. 
As  a  matter  of  fact  the  difference  is  less  great  than,  at 
first  sight,  appears  to  be  the  case.  The  lungs  of  the  toad 
are  composed  primarily  of  a  thin  membrane,  in  the  form 
of  a  sac,  richly  supplied  with  blood-vessels.  Air  is 
brought  to  this  thin  respiratory  membrane  and  by  osmosis 
the  oxygen  passes  through  the  membrane  and  through 
the  thin  walls  of  the  fine  blood-vessels,  and  is  taken  up 
by  the  blood.  At  the  same  time  the  carbonic  acid  gas 
brought  by  the  blood  to  the  lungs  from  all  parts  of  the 
body  is  given  up  by  it  and  passes  through  the  membranes 
in  order  to  leave  the  body.  The  air  comes  in  contact 
with  the  respiratory  membrane  (which  is  situated  inside 
the  body)  by  means  of  a  system  of  external  openings  and 
a  conducting  chamber,  and  by  these  same  openings  and 
chamber  the  carbonic  acid  gas  leaves  the  body.  In  the 
crayfish  the  gills  are  nothing  else  than  a  large  number  of 
small  flattened  sacs  each  composed  of  a  thin  membrane 


THE  MODIFICATION  OF  ORGANS  AND  FUNCTIONS      29 

richly  supplied  with  blood-vessels.  This  respiratory  mem- 
brane is  not,  in  the  crayfish,  situated  inside  the  body,  but 
on  the  outer  surface,  although  protected  by  being  in  a  sort 
of  pocket  with  a  covering  flap,  and  it  comes  into  immediate 
contact  with  the  air  held  in  the  water  which  freely  bathes 
the  gills.  By  osmosis  the  oxygen  of  this  air  passes  in 
through  the  gill-membranes,  while  the  carbonic  acid  gas 
brought  by  the  blood  passes  out  through  them.  Exactly 
the  same  exchange  of  gases  is  accomplished  as  in  the 
toad.  But  because  of  the  great  difference  in  the  conditions 
of  life  of  the  toad  and  crayfish,  one  living  in  \vater,  the 
other  living  out  of  water,  the  character  of  the  performance 
of  the  function  of  respiration,  and  correspondingly  the 
structural  condition  of  the  organs  performing  this  function, 
are  strikingly  different. 

Modification  of  functions  and  structure  to  fit  the 
animal  to  special  conditions  of  its  life. — As  has  been 
done  with  the  organs  of  digestion,  circulation,  and 
respiration,  so  we  might  compare  the  other  organs  of  the 
crayfish  and  the  toad.  There  would  be  found  not  only 
many  very  marked  differences  between  organs  which  have 
the  same  general  function  in  the  two  animals,  but  we 
should  find  also  numerous  organs  in  the  toad  which  are 
not  present  at  all  in  the  crayfish,  and  conversely;  and  this 
means,  of  course,  that  the  toad  can  do  numerous  things, 
perform  numerous  functions,  which  the  crayfish  cannot, 
and,  conversely,  that  the  crayfish  does  some  things  which 
the  toad  cannot.  But  both  of  these  animals  agree  in 
possessing  in  common  the  capability  of  performing  those 
processes  such  as  taking  food,  breathing,  reproducing, 
etc.,  to  which  attention  has  been  called  as  being  indis- 
pensable to  all  animal  life.  These  processes,  however, 
are  performed  by  the  two  animals  in  different  ways  and 
the  organs  for  the  performance  of  these  processes,  although 
at  very  bottom  essentially  alike,  are  in  outer  and  super- 


3°  ELEMENTARY  ZOOLOGY 

ficial  details  of  position,  appearance  and  general  structure 
markedly  different.  Animals  are  fitted  to  live  in  different 
places  amid  different  surroundings  by  having  their  bodies 
modified  and  the  performance  of  their  life-processes  modi- 
fied to  suit  the  special  conditions  of  their  life. 

Vertebrate  and  invertebrate. — In  selecting  the  toad 
and  the  crayfish  as  the  first  animals  to  study  and  to  com- 
pare with  each  other,  we  have  chosen  representatives  of 
the  two  great  groups  into  which  the  complexly  organized 
animals  are  divided,  viz.,  the  group  of  backboned  or 
vertebrate  animals,  and  the  group  of  backboneless  or 
invertebrate  animals.  To  the  vertebrates  belong  all  those 
which  have  an  internal  bony  skeleton  (and  a  few  without 
such  a  skeleton)  and  which  have  also  an  arrangement  of 
body-organs  on  the  general  plan  of  the  toad's  body.  A 
conspicuous  feature  of  this  arrangement  is  the  situation  of 
the  spinal  cord  or  main  great  nerve-trunk  along  the  back 
or  dorsal  wall  of  the  animal,  and  inside  of  a  backbone. 
All  the  fishes,  batrachians  (frogs,  toads,  salamanders, 
etc.),  reptiles  (snakes,  lizards,  alligators,  etc.),  birds,  and 
mammals  (quadrupeds,  whales,  seals,  etc.)  belong  to  the 
vertebrates.  /  The  backboneless  or  invertebrate  animals 
have  no  internal  bony  skeleton  and  have  their  main  nerve- 
trunk  usually  along  the  ventral  wall  of  the  body,  some- 
times in  a  circle  around  the  mouth,  but  never  in  a  back- 
bone. To  the  invertebrates  belong  all  insects,  lobsters, 
crabs,  clams,  squids,  snails,  worms,  starfishes  and  sea- 
urchins,  corals  and  sponges,  altogether  a  great  host  of 
animals,  mostly  small. 


7 


CHAPTER   VI 
AMCEBA   AND    PARAMCECIUM 

LABORATORY   EXERCISE 

Amoeba. — TECHNICAL  NOTE. — Amoeba  are  found  in  stagnant 
pools  of  water  on  the  dead  leaves,  sticks  and  slime  at  the  bottom. 
To  obtain  them,  collect  slime  and  water  from  various  puddles  in  sepa- 
rate bottles  and  take  them  to  the  laboratory.  Place  a  small  drop  of 
slime  on  a  slide  under  a  cover-glass.  Examine  under  the  low  power 
first  and  note  any  small  transparent  or  opalescent  objects  in  the 
field.  Examine  these  objects  with  the  higher  power  and  note  that 
some  are  mere  granular  jelly-like  specks,  which  slowly  (but  con- 
stantly) change  their  form.  These  are  Amoeba. 

A  teacher  of  zoology  recommends  the  following  method  of  obtain- 
ing a  large  supply  of  A  mceba :  "For  rearing  Ama'ba  place  two  or 
three  inches  of  sand  in  a  common  tub,  which  is  then  filled  with 
water  and  placed  some  feet  from  a  north  window  ;  three  or  four 
opened  mussels,  with  merest  trace  of  the  mud  from  the  stream  in 
which  they  are  taken,  are  partially  buried  in  the  sand  and  a  hand- 
ful of  Xitclla  and  a  couple  of  crayfish  cut  in  two  are  added  ;  as 
decomposition  goes  on  a  very  gentle  stream  is  allowed  to  flow  into 
the  tub,  and  after  from  two  to  four  weeks  abundant  Amoeba  are  to 
be  found  on  the  surface  of  the  sand  and  in  the  scum  on  the  sides  of 
the  tub  ;  small  Amoeba  appear  at  first,  and  later  the  large  ones." 

Having  found  an  Amaba  (fig.  5)  note  its  irregular 
shape,  and  if  it  moves  actively  observe  its  method  of  mov- 
ing. How  is  this  accomplished  ?  The  viscous,  jelly-like 
substance  which  composes  the  whole  body  of  an  Amceba 
is  called  protoplasm.  The  little  processes  which  stick 
out  in  various  directions  are  the  "false  feet"  (pseudo- 
podia).  Note  that  the  outer  portion,  the  cctosarc,  of  the 
protoplasmic  body  is  clear,  while  the  inner,  the  endosarc, 
is  more  or  less  granular  in  structure.  Has  Amoeba  a 
definite  body- wall  ?  Do  the  pseudopodia  protrude  only 

3' 


32  ELEMENTARY  ZOOLOGY 

from  certain  parts  of  the  body  ?  Within  the  endosarc 
note  a  clear  globular  spot  which  contracts  and  expands, 
or  pulsates,  more  or  less  regularly.  This  is  the  contrac- 
tile vacuole.  Note  the  small  granules  which  move  about 
within  the  endosarc.  These  are  food-particles  which 


FIG.  5. — Amceba  sp. ;  showing  the  forms  assumed  by  a  single  individual  in 
four  successive  changes.      (From  life.) 

have  been  taken  in  through  the  body-wall.  Note  how 
pseudopodia  flow  about  food-particles  in  the  water  and 
how  these  are  digested  by  the  protoplasm.  If  an  Amoeba 
comes  into  contact  with  a  particle  of  sand,  note  how  it  at 
once  retreats.  Note  within  the  endosarc  an  oval  trans- 
parent body  which  shows  no  pulsations.  This  is  the 


AMCEBA  /IND  PARAMCECIUM  33 

nucleus,  a  very  complex  little  structure  of  great  impor- 
tance in  the  make-up  of  Amceba. 

Note  that  A moeba  has  no  mouth  or  alimentary  canal; 
no  nostrils  or  lungs,  no  heart  or  blood-vessels,  no  mus- 
cles, no  glands.  It  is  an  animal  body  not  made  up  of 
distinct  organs  and  diverse  tissues.  Its  whole  body  is  a 
simple  minute  speck  of  protoplasm,  a  single  animal  cell. 
But  it  takes  in  food,  it  moves,  it  excretes  waste  matter 
from  the  body,  is  sensitive  to  the  touch  of  surrounding 
objects,  and,  as  we  may  be  able  to  see,  it  can  reproduce 
itself,  i.e.,  produce  new  Amcebce.  Amoeba  is  the  simplest 
living  animal. 

It  is  only  rarely  that  we  can  find  an  Amoeba  actually 
reproducing.  The  process,  in  its  gross  features,  is  very 
simple.  First  the  Amoeba  draws  in  all  of  its  pseudopodia 
and  remains  dormant  for  a  time.  Next,  certain  changes 
take  place  in  the  nucleus,  which  divides  into  equal  por- 
tions, one  part  withdrawing  to  one  end  of  the  protoplasmic 
body,  the  other  to  the  opposite  end.  Soon  the  body  pro- 
toplasm itself  begins  to  divide  into  two  parts,  each  part 
collecting  about  its  own  half  of  the  nucleus.  Finally  the 
two  halves  pull  entirely  away  from  each  other  and  form 
two  new  Amoebce^  each  like  the  original,  but  only  half  as 
large.  This  is  the  simplest  kind  of  reproduction  found 
among  animals. 

Amoeba  continue  to  live  and  multiply  as  long  as  the 
conditions  surrounding  them  are  favorable.  But  when 
the  pond  dries  up  the  Amcebcz  in  it  would  be  exterminated 
were  it  not  for  a  careful  provision  of  nature.  When  the 
pond  begins  to  dry  up  each  Amoeba  contracts  its  pseudo- 
podia  and  the  protoplasm  secretes  a  horny  capsule  about 
itself.  It  is  now  protected  from  dry  weather  and  can  be 
blown  by  the  winds  from  place  to  place  until  the  rains 
begin,  when  it  expands,  throws  off  the  capsule  and  com- 
mences active  life  again  in  some  new  pond. 


34  ELEMENTARY  ZOOLOGY 

The  Slipper  Animalcule  (Paramcccium  sp.)  —  TECHNICAL 
NOTE. — Paramcecia  can  be  secured  in  most  pond  water  where 
leaves  or  other  vegetation  are  decaying.  However,  if  specimens 
are  not  readily  secured  place  some  hay  or  finely  cut  dry  clover  in  a 
glass  dish,  cover  with  water  and  leave  in  the  sun  for  several  days. 
In  this  mixture  specimens  will  develop  by  thousands.  Place  a  drop 
of  water  containing  Paramcecia  on  a  slide  with  cover-glass  over  it. 
Using  a  low  power,  note  the  many  small  animals  darting  hither  and 
thither  in  the  field.  Run  a  thin  mixture  of  cherry  gum  in  water 
under  the  cover-glass.  In  this  mixture  they  can  be  kept  more  quiet 
and  be  better  studied. 

How  does  Paramcccium  (fig.  6)  differ  from  Amoeba  in 
form  and  movement  ?  Has  the  body  an  anterior  and  a 
posterior  end  ?  The  delicate,  short,  thread-like  processes, 
on  the  surface  of  the  body,  which  beat  about  very  rapidly 
in  the  water  are  called  cilia,  and  they^are  simply  fine 
prolongations  of  the  body  protoplasm.  ^What  is  their 
function  ?  Note  a  fine  cuticle  covering  the  body.  Note 
also  many  minute  oval  sacs  lying  side  by  side  in  the 
ectosarc.  These  are  called  trichocysts  and  from  each  a 
fine  thread  can  be  thrust  out. 

Note  on  one  side,  beginning  at  the  anterior  end,  the 
buccal  groove  leading  into  the  interior  through  the  gullet. 
Observe  also  that  by  the  action  of  the  cilia  in  the  buccal 
groove  food-particles  are  swept  into  the  gullet.  Rejected 
or  waste  particles  are  ejected  from  the  body  occasionally. 
Where  ?  Note  about  midway  of  the  Paramcecium  an 
ovoid  body  with  a  smaller  oval  one  attached  to  its  side, 
the  forme^  being  the  macronucleus,  the  latter  the  micro- 
uuclcus.  Note  that  there  are  two  contractile  vacuoles  in 
the  Paramcccium;  also  that  the  food-vacuoles  have  a 
definite  course  in  their  movement  inside  the  endosarc. 

Make  a  drawing  of  a  Paramcccium. 

In  comparing  Paramcccium  vyith  Amccba  it  is  apparent 
that  the  body  of  the  first  is  less  simple  than  that  of  the 
second.  The  definite  opening  for  the  ingress  of  food,  the 
two  nuclei,  the  fixed  cilia,  and  the  definite  cell-wall  giving 


AMCEBA  AND  PARAMCECIUM 


35 


a  fixed  shape  to  the  body,  are  all  specializations  which 
make  Paramcecium  more  complex  than  Amoeba.  But  the 
whole  body  is  still  composed  of  a  single  cell,  and  there 
is,  as  in  Amoeba,  no  differentiation  of  the  body-substance 
into  different  tissues,  and  no  arrangement  of  body-parts 
as  systems  of  organs. 

Paramcecium  may  occasionally  be  found  reproducing. 
This  process  takes  place  very 
much  as  in  Amoeba.  The  animal 
remains  dormant  for  a  while,  the 
micronucleus  then  divides,  the 
macronucleus  elongates  and 
finally  divides  in  two,  the  proto- 
plasm of  the  body  becomes  con- 
stricted into  two  parts,  each  part 
massing  itself  about  thewithdrawn 
halves  of  the  macro-  and  micro- 
nuclei,  and  lastly  the  whole  breaks 
into  two  smaller  organisms  which 
grow  to  be  like  the  original. 
After  multiplication  or  reproduc- 
tion has  gone  on  in  this  way  for 
numerous  generations  (about  one 
hundred),  a  fusion  of  two  Para- 
mcecia  seems  necessary  before 
further  divisions  take  place.  This 
process  of  fusion,  called  conjuga- 
tion, may  be  noted  at  some  sea- 
sons, 
their  buccal  grooves  together, 


~,  ....     FIG.    6.  —  Parama'chim    sp.  ; 

1  wo  Paramcrcia  unite  with      buccal  groove  at  right.  (From 

life.) 


part  of  the  macronucleus  and  micronucleus  of  each  passes 
over  to  the  other,  and  the  irjxed  elements  fuse  together 
to  form  a  new  macro-  and  micronucleus  in  each  half. 
The  conjugating  Paramcccia  now  separate,  and  each 
divides  to  form  two  new  individuals. 


CHAPTER    VII 

THE    SINGLE-CELLED    ANIMAL    BODY.— PRO- 
TOPLASM   AND    THE   CELL 

The  single-celled  body. — The  study  of  Amoeba  and 
Paramcecium  has  made  us  acquainted  with  an  animal  body 
very  different  from  that  of  the  toad  or  the  crayfish.  These 
extraordinarily  minute  animals  have  a  body  so  simple  in 
its  composition,  compared  with  the  toad's,  that  if  the 
toad's  body  be  taken  for  the  type  of  the  animal  body, 
Amoeba  might  readily  be  thought  not  to  be  an  animal  at 
all.  The  body  of  Amoeba  is  not  composed  of  organs,  each 
with  a  particular  function  or  work  to  perform.  Whatever 
an  Amoeba  does  is  done,  we  may  say,  with  its  whole  body. 
But  as  we  learn  the  things  that  this  formless  viscid  speck 
of  matter  does,  we  see  that  it  is  truly  an  animal ;  that  it 
really  does  those  things  which  we  have  learned  are  the 
necessary  life-processes  of  an  animal.  Amoeba  takes  up 
and  digests  food  composed  of  organic  particles;  it  has  the 
power  of  motion ;  it  knows  when  its  body  comes  in  con- 
tact with  some  external  object,  that  is,  it  can  feel  or  has 
the  power  of  sensation.  Amoeba  takes  in  oxygen  and 
gives  out  carbonic  acid  gas,  and  it  can  produce  new  in- 
dividuals like  itself,  that  is,  it  has  the  power  of  reproduc- 
tion. But  for  the  performance  of  these  various  life-pro- 
cesses or  functions  it  has  no  special  parts  or  organs,  no 
mouth  or  alimentary  canal,  no  lungs  or  gills,  no  legs,  no 
special  reproductive  organs.  We  have  here  to  do  with  one 
of  the  "simplest  animals."  With  a  minute,  organless, 

36 


THE  SINGLE-CELLED  AWMAL  BODY  37 

soft  speck  of  viscous  matter  called  protoplasm  for  a  body, 
the  simplest  structural  condition  to  be  found  among  living 
beings,  Amoeba  nevertheless  is  capable  of  performing,  in 
the  simplest  way  in  which  they  may  be  performed,  those 
processes  which  are  essential  to  animal  life. 

Paramcecium  has  a  body  a  little  less  simple  than 
Amoeba.  The  food-particles  are  taken  into  the  body 
always  at  a  certain  spot;  this  might  be  spoken  of  as  a 
mouth.  And  the  body  has  some  special  locomotory 
organs,  if  they  may  be  so  called,  in  the  presence  of  the 
cilia.  The  body,  too,  has  a  definite  shape  or  form. 
But,  as  in  Amoeba,  there  is  no  alimentary  canal,  nor 
nervous  system,  nor  respiratory  system,  nor  reproductive 
system.  The  whole  body  feels  and  breathes  and  takes 
part  in  reproduction. 

A  long  jump  has  been  made  from  the  toad  and  crayfish 
to  Amoeba  and  Paramoecium;  from  the  complex  to  the 
simplest  animals.  But,  as  will  later  be  seen,  the  great 
difference  between  the  bodies  of  these  simplest  animals 
and  those  of  the  highly  complex  ones  is  only  a  difference 
of  degree ;  there  are  animals  of  all  grades  and  stages  of 
structural  condition  connecting  the  simplest  with  the  most 
complex.  When  animals  are  studied  systematically,  as 
it  is  called,  we  begin  with  the  simplest  and  proceed  from 
them  to  the  slightly  complex,  from  these  to  the  more 
complex,  and  finally  to  the  most  complex.  There  are 
hundreds  of  thousands  of  different  kinds  of  animals,  and 
they  represent  all  the  degrees  of  complexity  which  lie 
between  the  extremes  we  have  so  far  studied. 

The  cell. — The  characteristic  thing  about  the  body  of 
Amccba  and  Paramcecium  and  the  other  "simplest 
animals  ' '  — for  there  are  many  members  of  the  group  of 
"simplest  animals,"  or  Protozoa — is  that  it  is  com- 
posed, for  the  animal's  whole  lifetime,  of  a  single  cell. 
A  cell  is  the  structural  unit  of  the  animal  body.  As 


38  ELEMENTARY  ZOOLOGY 

will  be  learned  in  the  next  exercise,  the  bodies  of  all 
other  animals  except  the  Protozoa,  the  simplest  animals, 
are  composed  of  many  cells.  These  cells  are  of  many 
kinds,  but  the  simplest  kind  of  animal  cell  is  that  shown 
by  the  body  of  an  Amoeba,  a  tiny  speck  of  viscous,  nearly 
colorless  protoplasm  without  fixed  form.  The  protoplasm 
composing  the  cell  is  differentiated  to  form  two  parts  or 
regions  of  the  cell,  an  inner  denser  part,  called  the 
nucleus,  and  an  outer  clearer  part,  called  the  cytoplasm. 
Sometimes,  as  in  the  Paramxcium,  the  cell  is  enclosed  by 
a  cell-wall  which  may  be  simply  a  denser  outer  layer  of 
the  cytoplasm,  or  may  be  a  thin  membrane  secreted  by 
the  protoplasm.  Thus  the  cell  is  not  what  its  name 
might  lead  us  to  expect,  typically  cellular  in  character; 
that  is,  it  is  not  (or  only  rarely  is)  a  tiny  sac  or  box  of 
symmetrical  shape.  While  the  cell  is  composed  essen- 
tially of  protoplasm,  yet  it  may  contain  certain  so-called 
cell-products,  small  quantities  of  various  substances  pro- 
duced by  the  life-processes  of  the  protoplasm.  These 
cell-products  are  held  in  the  protoplasmic  body-mass  of 
the  cell,  and  may  consist  of  droplets  of  water  or  oil  or  resin, 
or  tiny  particles  of  starch  or  pigment,  etc.  The  cell 
cannot  be  said  to  be  composed  of  organs,  because  the 
word  organ,  as  it  is  commonly  used  in  the  study  of  an 
animal,  is  understood  to  mean  a  part  of  the  animal  body 
which  is  composed  of  many  cells.  But  the  single  cell 
can  be  somewhat  differentiated  into  parts  or  special 
regions,  each  ^art  or  special  region  being  especially 
associated  with  some  one  of  the  life-processes.  In 
Paramoecium,  for  example,  the  food  is  always  taken  in 
through  the  so-called  mouth-opening;  the  fine  proto- 
plasmic cilia  enable  the  cell  to  swim  freely  in  the  water, 
the  waste  products  of  the  body  are  always  cast  out  through 
a  certain  part,  and  so  on.  But  this  is  a  very  simple  sort 
of  differentiation,  and  the  whole  body  is  only  one  of  those 


THE  SINGLE-CELLED  ANIMAL  BODY  39 

structural  units,  the  cells,  of  which  so  many  are  included 
in  the  body  of  any  one  of  the  complex  animals. 

Protoplasm. — The  protoplasm,  which  is  the  essential 
substance  of  the  typical  animal  cell  and  hence  of  the 
whole  animal  body,  is  a  substance  of  very  complex 
chemical  and  physical  make-up.  No  chemist  has  yet 
been  able  to  determine  its  exact  chemical  constitution, 
and  the  microscope  has  so  far  been  unable  to  reveal 
certainly  its  physical  characters.  The  most  important 
thing  known  about  the  chemical  constitution  of  proto- 
plasm is  that  there  are  always  present  in  it  certain  com- 
plex albuminous  substances  which  are  never  found  in 
inorganic  bodies.  And  it  is  certain  that  it  is  on  the 
presence  of  these  substances  that  the  power  possessed 
by  protoplasm  of  performing  the  fundamental  life-pro- 
cesses depends.  Protoplasm  is  the  primitive  physical 
basis  of  life,  but  it  is  the  presence  of  the  complex  albu- 
minous substances  in  it  that  makes  it  so. 

The  physical  constitution  of  protoplasm  seems  to  be 
that  of  a  viscous  liquid  containing  many  fine  globules  of  a 
liquid  of  different  density  and  numerous  larger  globules 
of  a  liquid  of  still  other  density.  Some  naturalists  believe 
the  fine  globules  to  be  solid  grains,  while  still  others 
believe  that  numerous  fine  threads  of*  dense  protoplasm 
lie  coiled  and  tangled  in  the  clearer,  viscous  protoplasm. 
But  the  little  we  know  of  the  physical  structure  of  proto- 
plasm thro\vs  almost  no  light  on  the  remarkable  properties 
of  this  fundamental  life-substance. 


CHAPTER    VIII 

CELLULAR  STRUCTURE  OF  THE  TOAD  (OR 

FROG) 

LABORATORY   EXERCISE 

The  blood. — TECHNICAL  NOTE. — The  blood  of  a  frog  can  be 
studied  as  it  flows  through  the  small  vessels  in  the  membranes 
between  the  toes  while  the  animal  is  alive.  Place  a  frog  on  a  small 
flat  board  which  has  had  a  hole  cut  near  one  end,  and  with  a 
piece  of  cloth  bind  it  to  the  board.  Spread  the  web  between  two 
toes  over  the  hole  in  the  board  and  keep  it  in  place  with  pins. 
This  done,  examine  the  distended  web  under  the  compound  micro- 
scope first  with  low  then  with  higher  power,  and  observe  the  blood- 
vessels and  the  blood  circulating  in  them.  For  a  further  study  of 
the  blood  kill  a  toad  or  frog  and  place  a  drop  of  the  blood  on  a 
slide  with  a  cover-glass  over  it. 

Put  the  prepared  slide  under  the  microscope  and  note 
that  the  blood,  which  as  seen  with  the  unaided  eye 
appears  to  be  a  red  fluid,  is  made  up  of  a  great  many 
yellowish  elliptical  disks  or  cells,  the  blood-corpuscles, 
floating  in  a  liquid,  the  blood-plasma.  Here  and  there 
you  may  notice  amoeboid  blood-corpuscles.  These  are 
irregular-shaped  cells  which  move  about  by  thrusting  out 
pseudopodia.  They  look  like  some  of  the  unicellular 
animals,  as  the  Amccba.  Can  you  distinguish  a  nucleus 
and  cell-wall  in  the  blood-cells  ? 

Make  drawings  of  these  blood-cells. 

The  skin. — TECHNICAL  NOTE.— Keep  a  live  toad  or  frog  in 
water  for  some  time  and  note  if  its  skin  becomes  loose  or  begins  to 
slip  away.  If  the  outer  skin,  epidermis,  comes  off,  take  some  of  the 
shed  skin  and  wash  it  in  water,  then  stain  for  three  or  four  minutes 
in  a  solution  of  methyl-green  and  acetic  acid  (seep.  451).  Cut 

40 


CELLULAR  STRUCTURE  OF  THE   TOAD  (OR  FROG)      41 

the  pieces  of  stained  skin  into  small  bits  and  examine  one  of  these 
under  the  microscope. 

With  the  low  power  of  the  microscope  you  will  note 
that  the  skin  is  made  up  of  a  great  many  flat  cells  placed 
edge  to  edge.  Each  one  has  its  cell-wall  and  a  central 
darkly  stained  nucleus. 

Make  a  drawing  of  a  portion  of  the  toad's  skin. 

The  liver. — TECHNICAL  NOTE. — Cut  through  the  fresh  liver 
of  a  toad,  and  with  a  knife-blade  scrape  from  the  cut  surface  some 
of  the  liver-cells  and  place  them  on  a  slide  with  cover-glass. 

Examine  under  the  microscope  and  observe  many 
polygonal  cells.  Place  some  of  the  methyl-green  acetic 
stain  under  the  cover-glass  and  note,  after  the  cells  are 
stained,  that  they  have  definite  boundaries  and  a  central 
nucleus. 

Draw  some  of  these  scattered  liver-cells. 

The  muscles. — TECHNICAL  NOTE.— Take  a  piece  of  intestine 
from  a  freshly  killed  toad,  wash  it  thoroughly  and  place  it  in  a  con- 
centrated solution  of  salicylic  acid  in  70%  alcohol  for  24  hours, 
then  gradually  heat  until  about  the  boiling-point,  when  the  muscles 
will  fall  to  pieces.  Transfer  the  preparation  to  a  watch-crystal  and 
tease  small  bits  of  isolated  muscle  with  dissecting-needles.  Place 
some  of  the  teased  muscle-fibres  on  a  slide,  cover  with  cover-glass, 
and  add  a  drop  of  the  methyl-green  acetic  acid. 

'  Note  the  small  spindle-shaped  muscle-fibres.  Each 
one  of  these  fibres  is  a  cell  possessing  all  of  the  structures 
common  to  cells,  namely,  cell-wall,  nucleus,  etc. 

Make  a  drawing  of  a  few  isolated  fibres  of  muscle. 

From  this  study  of  some  of  the  tissues  in  a  toad  it  will 
be  noted  that  in  the  first  case  we  had  in  the  blood 
separate  cells  which  moved  about  freely  in  the  plasma. 
In  the  second  case,  that  of  the  epidermis,  the  cells  are 
fixed  edge  to  edge,  thus  forming  a  thin  tissue;  while  in 
the  third  and  fourth  cases,  that  of  the  liver  and  muscle, 
the  cells  are  not  only  placed  edge  to  edge,  but  aggregated 


42  ELEMENTARY  ZOOLOGY 

into  vast  masses  or  bundles,  in  one  case  to  form  the  liver 
and  in  the  other  case  a  muscle.  The  entire  body  of  the 
toad  is  built  up  of  a  colony  of  simple  units  (cells)  com- 
bined in  various  forms  to  make  all  the  various  tissues  and 
organs. 


CHAPTER   IX 

THE     MANY-CELLED     ANIMAL    BODY. —DIF- 
FERENTIATION   OF    THE    CELL 

The  many-celled  animal  body. — In  the  study  of  cer- 
tain of  the  tissues  and  organs  of  the  toad  we  have  learned 
that  the  body  of  this  animal  is  composed  of  many  cells, 
thousands  and  thousands  of  these  microscopic  structural 
units  being  combined  to  form  the  whole  toad.  This 
many-celled  or  multicellular  condition  of  the  body  is  true 
of  all  the  animals  except  the  simplest,  the  unicellular 
Protozoa.  Corals,  starfishes,  worms,  clams,  crabs,  in- 
sects, fishes,  frogs,  reptiles,  birds,  and  mammals,  all  the 
various  kinds  of  animals  in  which  the  body  is  composed 
of  organs  and  tissues,  agree  in  the  multicellular  character 
of  the  body,  and  may  be  grouped  together  and  called  the 
many-celled  animals  in  contrast  to  the  one-celled  animals. 
This  division  is  one  which  is  recognized  by  many  syste- 
matic zoologists  as  being  more  truly  primary  or  funda- 
mental than  the  division  of  animals  into  Vertebrates  and 
Invertebrates.  The  one-celled  animals  are  called  Pro- 
tozoa, and  the  many-celled  animals  Metazoa. 

Differentiation  of  the  cell. — It  is  apparent  at  first 
glance  that  the  cells  which  compose  the  body  of  a  many- 
celled  animal  are  not  like  the  simple  primitive  cell  which 
makes  up  the  body  of  the  Amoeba ,  nor  are  they  like  the 
more  complexly  arranged  cell  of  the  Paramoecium.  Nor 
are  they  all  like  each  other.  The  cells  in  the  toad's  blood 
are  of  two  kinds,  the  white  blood-cells,  which  are  very  like 


44  ELEMENTARY  ZOOLOGY 

the  body  of  Amoeba,  and  the  elliptical  disk-like  red  blood- 
cells.  The  cells  composing  the  muscles  are,  moreover, 
like  neither  kind  of  blood-cells,  and  the  cells  of  which  the 
liver  is  composed  are  not  like  the  cells  of  the  muscles. 
That  is,  there  are  many  different  kinds  of  cells  in  the  body 
of  a  many-celled  animal.  While  the  single  cell  which 
composes  the  whole  body  of  the  Amoeba  is  able  to  do  all 
the  things  necessary  to  maintain  life,  the  various  cells  in  the 
body  of  a  complex  animal  are  differentiated  or  specialized, 
certain  cells  devoting  themselves  to  a  certain  function  or 
special  work,  and  others  to  other  special  functions.  For 
example,  the  cells  which  compose  the  organs  of  the 
nervous  system,  the  brain,  ganglia,  and  nerves,  devote 
themselves  almost  exclusively  to  the  function  of  sen- 
sation, and  they  are  especially  modified  for  this  purpose. 
The  highly  specialized  nerve-cells  resemble  very  little  the 
primitive  generalized  body-cell  of  Amoeba.  The  muscle- 
cells  of  the  complex  animal  body  have  developed  to  a 
high  degree  that  power  of  contraction  which  is  possessed, 
though  in  but  slight  degree,  by  Amoeba.  These  muscle- 
cells  have  for  their  special  function  this  one  of  contraction, 
and  massed  together  in  great  numbers  they  form  the 
strongly  contractile  muscular  tissue  and  muscles  of  the 
body  on  which  the  animal's  power  of  motion  depends. 
The  cells  which  line  certain  parts  of  the  alimentary  canal 
are  the  ones  on  which  the  function  of  digestion  chiefly 
rests.  And  so  we  might  continue  our  survey  of  the 
whole  complex  body.  The  point  of  it  all  is  that  the 
thousands  of  cells  which  compose  the  many-celled  animal 
body  are  differentiated  and  specialized;  that  is,  have 
become  changed  or  modified  from  the  generalized  primitive 
amoeboid  condition,  so  that  each  kind  of  cell  is  devoted 
to  some  special  work  or  function  and  has  a  special  struc- 
tural character  fitting  it  for  its  special  function.  In  the 
Protozoan  body  the  single  cell  can  perform  and  does  per- 


DIFFERENTIATION  OF  THE  CELL  45 

form  all  the  functions  or  processes  necessary  to  the  life  of 
the  animal.  In  the  Metazoan  body  each  cell  performs,  in 
co-operation  with  many  other  similar  cells,  some  one 
special  function  or  process.  The  total  work  of  all  the 
cells  is  the  living  of  the  animal. 


CHAPTER    X 
HYDRA 

LABORATORY   EXERCISE 

TECHNICAL  NOTE. — Hydra  lives  in  fresh  water,  attached  to  stones, 
sticks,  or  decayed  leaves.  It  can  be  found  in  most  open  fresh-water 
ponds  not  too  stagnant,  often  attached  to  Chara.  There  are  two 
species  occurring  commonly,  H.  iriridis,  the  green  Hydra,  and  H. 
fuscus,  the  brown  or  flesh-colored  Hydra.  Both  are  very  small 
forms  and  have  to  be  looked  for  carefully.  Specimens  should  be 
brought  to  the  laboratory,  put  into  a  large  dish  of  water  and  left 
in  the  light.  Hydra  is  best  studied  alive.  Place  a  living  specimen 
attached  to  a  bit  of  weed  in  a  watch-crystal  filled  with  water  or  on 
a  slide  with  plenty  of  water  and  examine  with  the  low  power  of  the 
microscope. 

Note  the  cylindrical  body  (fig.  7,  A,  E)  with  its  flat 
basal  attachment  and  radial  tentacles  (varying  in  number) 
which  crown  the  upper  end  and  surround  the  centrally 
located  mouth.  Note  the  movements  of  Hydra,  its  powers 
of  contraction,  and  method  of  taking  in  food. 

TECHNICAL  NOTE. — -To  feed  Hydra,  place  very  small  "  water- 
fleas"  (Daphuia  sp. )  in  the  water  with  it. 

Observe  the  method  by  which  "  water-fleas  "  are  taken 
into  the  mouth.  Food  is  caught  on  stinging  cells  (to  be 
studied  later)  and  conveyed  to  the  mouth  by  the  tenta- 
cles. Note  that  the  cylindrical  body  encloses  a  cavity, 
the  digestive  cavity.  How  is  this  connected  with  the  ex- 
terior ?  If  Hydra  captures  prey  too  large  or  is  no  longer 
hungry,  the  prey  is  released. 

46 


HYDRA 


47 


'•'"•"•' -•'  lth    0 

,,,.,-  .  V 


E 


FIG.  7  — A,  Hydra  fusca,  with  expanded  body  and  a  budding  individual; 
B,  H.fiaca,  contracted;  C,  H.  fusca.  part  of  outer  surface  of  a  tenta- 
cle, greatly  magnified.  (A  and  B  drawn-  from  live  specimens.  C,  from  a 
preparatio'i;  )'l),  Grantia  sp.  (a  sponge),  three  individuals;  E,  Gruntia^ 
sp.,  longitudinal  section  ;  F,  Grunlin  sp.,  spicules.  (D,  E,  and  F 
drawn  from  preserved  specimens. ) 


48  ELEMENTARY  ZOOLOGY 

TECHNICAL  NOTE. — Place  small  slips  of  paper  on  the  slide  near 
the  Hydra,  put  cover-glass  over  the  whole,  and  examine  with  the 
low  power  of  the  microscope. 

Note  that  the  whole  animal  is  made  up  of  cells  closely 
joined.  Are  the  cells  in  the  tentacles  all  alike  ?  Note 
nodule-like  projections  above  some  of  the  cells;  these  are 
stinging  cells,  or  cnidoblasts.  In  some  cases  a  small  hair- 
like  process,  the  trigger  hair  or  cnidocil,  may  be  seen  pro- 
jecting above  the  surface  of  the  cell.  Note  in  some  of  the 
tentacles  dark-colored  particles.  These  are  food-particles 
which  have  been  taken  through  the  mouth  into  the  diges- 
tive cavity  and  have  passed  thence  into  the  tentacles. 
The  central  digestive  cavity  communicates  freely  with  the 
cavities  in  the  tentacles,  for  the  tentacles  are  merely 
evaginations  of  the  body-wall. 

Make  drawings  of  the  Hydra  expanded  and  of  the  same 
individual  contracted.  r 

TECHNICAL  NOTE. — From  the  preparation  which  you  have  under 
the  microscope  pull  out  the  slips  of  paper,  thus  letting  the  cover- 
glass  drop  down  on  the  specimen.  With  a  small  pipette  put  a 
drop  of  anilin-acetic  stain  (see  p.  451 )  on  the  slide  at  one  side 
of  the  cover-glass  and  with  a  piece  of  filter-paper  draw  the  water 
through  from  the  other  side  of  the  cover-glass.  When  the  stain  is 
diffused  press  down  the  cover-glass  gently  and  examine  the  tentacles 
first  under  a  low  power  of  the  microscope,  then  under  a  high  one. 

Note  the  distortion  that  the  animal  has  undergone 
through  the  action  of  the  reagent.  Observe  the  cnido- 
blasts  of  the  tentacles  and  note  that  many  of  them  have 
thrown  out  long  whip-like  processes  (fig.  7,  C).  On 
what  parts  of  the  body  do  the  cnidoblasts  occur  ?  Care- 
fully examine  one  of  the  cnidoblasts  which  has  been  dis- 
charged and  note  a  clear  transparent  bag-like  structure 
within,  the  nematocyst,  to  which  is  attached  the  long 
whip-like  process.  In  another  cnidoblast  cell  which  has 
not  been  discharged  note  that  the  whip-like  process  is 
coiled  about  inside  of  the  bag-like  structure.  The  whole 


HYDRA  49 

apparatus  is  like  the  inturned  finger  of  a  glove  which  can 
be  blown  out  by  pressure  from  the  inside.  The  mechan- 
ism is  simple.  The  cnidocil  or  trigger-hair  is  touched  by 
some  animal,  an  impulse  is  conveyed  to  the  delicate  fibres 
interspersed  among  the  cells  (nerve-cells)  which  stimulate 
the  cnidoblast  cell,  whereupon  there  is  a  contraction  of 
the  contents  and,  the  cnidoblast  being  compressed,  the 
inverted  whip-like  process  turns  wrong  side  out  and  im- 
pales the  animal  on  its  points  or  barbs. 

TECHNICAL  NOTE. — The  teacher  should  be  provided  with  micro- 
scopical sections,  both  transverse  and  longitudinal,  of  the  Hydra 
stained  in  some  good  general  stain  (hsematoxylin  or  borax  carmine). 
If  the  teacher  has  no  means  of  making  such  preparations,  they  may 
be  procured  from  dispensers  of  microscopical  supplies. 

From  the  cross-section  of  the  Hydra  make  out  the 
general  structure  of  the  body.  Note  that  it  is  a  hollow 
cylinder  consisting  of  two  well-defined  layers  of  cells,  an 
outside  ectoderm  layer  and  an  inner  endoderm  layer. 
Between  these  two  is  yet  another  thin  non-cellular  layer 
called  the  mesogloea. 

Thus  it  will  be  seen  that  Hydra  is  made  up  of  two 
layers  of  cells,  the  outer  ectoderm  or  skin,  which  is 
specialized  to  perform  the  office  of  capturing  prey  as  well 
as  that  of  protection,  and  the  inner  endoderm,  whch  sur- 
rounds the  digestive  cavity  and  performs  the  function  of 
digestion.  The  endoderm  lines  the  body-cavity,  particles 
taken  in  as  food  being  digested  by  certain  digestive  cells 
which  thrust  out  amoeboid  processes  and  ingest  particles 
of  food.  Other  cells  in  the  endoderm  have  long  flagellate 
processes  which  vibrate  back  and  forth  in  the  digestive 
cavity,  thereby  creating  currents  in  the  water  containing 
food-particles. 

Note,  in  a  cross-section,  that  there  are  small  ovoid  or 
cuboid  cells  at  the  bases  of  the  large  ectoderm  cells. 
These  are  the  interstitial  cells.  Some  of  the  interstitial 


50  ELEMENTARY  ZOOLOGY 

cells  become  modified  and  pushed  up  between  the  ecto- 
derm cells  to  form  cnidoblast  cells.  Many  of  the 
endoderm  as  well  as  ectoderm  cells  have  muscle-processes 
which  spread  out  from  the  base  of  the  cell  and  which 
serve  to  contract  and  expand  the  body. 

TECHNICAL  NOTE. — In  the  specimens  which  have  been  collected 
perhaps  two  methods  of  reproduction  will  be  observed.  Place 
healthy  Hydrce  in  a  wide-mouthed  jar  in  the  sunlight  with  plenty 
of  water  and  food.  In  a  few  days  active  budding  will  take  place. 

Observe  the  method  of  reproduction  in  Hydra.  Com- 
monly the  parent  produces  small  buds,  which  at  first  are 
only  evaginations  of  the  body- wall,  but  which  later 
develop  tentacles  and  a  mouth  of  their  own.  Subse- 
quently the  bud  becomes  constricted  at  the  base,  separates 
from  the  parent,  and  the  young  Hydra  begins  a  distinct 
existence. 

Another  mode  of  reproduction  takes  place  which,  in 
distinction  from  the  asexual  method  just  mentioned,  is 
called  sexual  reproduction.  This  last  is  the  method 
common  to  most  of  the  higher  organisms.  You  may  note 
that  in  some  Hydra  there  is  a  swelling  or  bulging  of  the 
ectoderm  of  the  body-wall  in  the  region  just  below  the 
tentacles.  These  are  the  sperm-glands.  Within  these  are 
produced  sperm-cells  which  break  away  in  great  clusters 
to  fertilize  the  ova,  or  eggs.  Note  a  larger  bulging  of  the 
body-wall  nearer  the  lower  end  of  the  body  which,  under 
high  power,  has  a  granular  appearance.  This  is  the  egg- 
gland,  in  which  develops  a  single  ovum  or  egg.  The 
ovum  breaks  from  its  covering  and  is  fertilized  by  sperm- 
cells  from  another  individual.  In  forms  like  Hydra, 
where  both  sexes  are  represented  in  a  single  individual, 
the  organism  is  termed  vioiurcunis  or  hermaphroditic*  In 
connection  with  reproduction  Chapter  XIII  should  be 
studied. 


HYDRA  51 

An  instructive  experiment  can  be  performed  by  cutting 
a  Hydra  into  two  or  more  parts,  when  (usually)  each  of 
the  various  parts  will  develop  into  a  complete  Hydra. 
This  process  may  be  called  reproduction  by  fission,  but  it 
rarely  occurs  naturally, 


CHAPTER   Xt 
THE    SIMPLEST    MANY-CELLED    ANIMALS 

Cell  differentiation  and  body  organization  in  Hydra. 

—From  the  examination  of  Hydra  we  have  learned  that 
there  are  true  many-celled  animals  which  are  much  less 
complex  in  structure  than  the  toad  and  crayfish.  The 
body  of  Hydra,  like  the  body  of  the  toad,  is  composed  of 
many  cells,  but  these  cells  are  of  only  a  few  different 
kinds;  that  is,  show  but  little  differentiation.  There  is 
relatively  little  division  of  the  body  into  distinct  organs. 
Still,  certain  parts  of  the  body  devote  themselves  princi- 
pally to  certain  particular  functions.  Thus  all  the  food  is 
taken  in  through  the  single  "mouth-opening"  at  the 
apical  free  end  of  the  cylindrical  body,  and  there  are 
certain  organs,  the  tentacles,  whose  special  business  or 
function  it  is  to  find  and  seize  food  and  to  convey  it  to  the 
mouth.  After  the  food  is  taken  into  the  cylindrical  body- 
cavity  it  is  digested  by  special  cells  which  line  the  cavity. 
Some  of  these  cells  are  unusually  large,  and  each  contains 
one  or  more  contractile  vacuoles.  From  the  free  ends  of 
these  cells,  the  ends  which  are  next  to  the  body-cavity, 
project  pseudopods  or  flagella.  These  protoplasmic 
processes  are  constantly  changing  their  form  and  number. 
In  addition  to  these  large  sub-amoeboid  cells  there  are,  in 
this  inner  layer  of  cells  lining  the  body-cavity,  and 
especially  abundant  near  the  base  or  bottom  of  the  cavity, 
many  long,  narrow,  granular  cells.  These  are  gland- 
cells  which  secrete  a  digestive  fluid.  The  food  captured 
by  the  tentacles  and  taken  in  through  the  mouth-opening 
disintegrates  in  the  body-cavity,  or  digestive  cavity  as  it 

52 


THE  SIMPLEST  MANY-CELLED  ANIMALS  53 

may  be  called.  The  digestive  fluid  secreted  by  the 
gland-cells  acts  upon  it  so  that  it  becomes  broken  into 
small  parts.  These  particles  are  seized  by  the  projecting 
pseudopods  of  the  sub-amceboid  cells  and  taken  into  the 
body-protoplasm  of  these  cells.  The  cells  of  the  outer 
layer  of  the  body  do  not  take  food  directly,  but  receive 
nourishment  only  by  means  of  and  through  the  cells  of 
the  inner  layer.  The  body-cavity  of  Hydra  is  a  very 
simple  special  organ  of  digestion. 

In  the  outer  layer  of  cells  there  are  some  specially 
large  cells  whose  inner  ends  are  extended  as  narrow 
pointed  prolongations  directed  at  right  angles  with  the 
rest  of  the  cell.  These  processes  are  very  contractile  and 
are  called  muscle-processes.  Each  one  is  simply  a 
specially  contractile  continuation  of  the  protoplasm  of  the 
cell-body.  There  are  also  in  this  layer  some  small  cells 
very  irregular  in  shape  and  provided  with  unusually  large 
nuclei.  These  cells  are  more  irritable  or  sensitive  than 
the  others  and  are  called  nerve-cells.  We  have  thus  in 
Hydra  the  beginnings  of  muscular  organs  and  of  nerve- 
organs.  But  how  simple  and  unformed  compared  with 
the  muscular  and  nervous  systems  of  the  toad  and  crayfish  ! 
There  is  no  circulatory  system,  nor  are  there  any  special 
organs  of  respiration. 

But  Hydra  is  far  in  advance  of  Amoeba  or  Paramoccium. 
Its  body  is  composed  of  thousands  of  distinct  cells.  Some 
of  these  cells  devote  themselves  especially  to  food-taking, 
some  especially  to  the  digestion  of  food;  some  are 
specially  contractile,  and  on  them  the  movements  of  the 
body  depend,  while  others  are  specially  irritable  or  sensi- 
tive, and  on  them  the  body  depends  for  knowledge  of  the 
contact  of  prey  or  enemies.  In  the  cnidobla^t  cells,  those 
with  the  stinging  threads,  there  is  a  very  wide  departure 
from  the  simple  primitive  type  of  cells.  There  is  in 
Hydra  a  manifest  differentiation  of  the  cells  into  various 


54  ELEMENTARY  ZOOLOGY 

kinds  of  cells.      The  beginnings  of  distinct   tissues   and 
organs  are  indicated. 

Degrees  in  cell  differentiation  and  body  organization. 

—  In  the  study  of  the  cellular  constitution  of  the  tissues 
and  organs  of  the  toad,  we  found  to  what  a  high  degree 
the  differentiation  of  the  cells  may  attain,  and  in  the  study 
of  the  anatomy  of  the  toad  we  found  how  thoroughly  these 
differentiated  cells  may  be  combined  and  organized  into 
body-parts  or  organs.  The  body  of  the  toad  is  made  up 
of  distinct  organs,  each  composed  of  highly  differentiated 
or  specialized  cells.  The  body  of  Hydra  is  composed  of 
cells  for  the  most  part  only  slightly  differentiated  and 
hardly  recognizably  grouped  or  combined  into  organs. 
These  two  conditions  are  the  extremes  in  the  body- 
structure  of  the  many-celled  animals.  Between  them 
is  a  host  of  intermediate  conditions  of  cell  differentia- 
tion and  body  organization.  When  we  come  to  the 
study  of  other  members  of  the  great  branch  of  simple 
many-celled  animals  to  which  Hydra  belongs  (see 
Chapter  XVII),  it  will  be  found  that  some  of  them 
show  a  slight  advance  in  complexity  beyond  Hydra. 
Higher  in  the  scale  of  animal  life  the  forms  will  be  found 
still  more  and  more  complex,  with  ever-increasing  differ- 
entiation of  the  cells,  with  the  combination  of  the  differ- 
entiated cells  into  distinct  organs,  and  the  co-ordination 
of  organs  into  systems  of  organs  up  to  the  extreme  shown 
by  the  birds  and  mammals.  And  hand  in  hand  with  this 
increasing  complexity  of  structure  goes  ever-increasing 
complexity  or  specialization  of  function.  Breathing  is  a 
simple  function  or  process  with  Hydra,  where  each  body- 
cell  takes  up  oxygen  for  itself,  but  it  is  a  complex  business 
with  the  toad,  or  with  a  bird  or  mammal,  where  certain 
complex  structures,  the  lungs  and  accessory  parts,  and 
the  heart,  blood-vessels  and  blood  all  work  together  to 
distribute  oxygen  to  all  parts  of  the  body. 


CHAPTER    XII 
DEVELOPMENT    OF    THE    TOAD 

FIELD   AND   LABORATORY   EXERCISE 

TECHNICAL  NOTE. — As  the  work  of  this  chapter,  or  some  similar 
work  in  getting  acquainted  with  the  postembryonic  development 
of  a  many-celled  animal,  should  be  done  early  in  the  course,  and 
as  most  schools  open  in  the  fall,  it  will  perhaps  be  impossible  to 
make  this  first  study  of  development  from  live  specimens  in  the  field. 
In  such  case  the  examination  of  a  series  of  prepared  specimens, 
previously  obtained  by  the  teacher,  must  be  resorted  to.  In  the 
spring  the  development  of  several  kinds  of  animals,  including  the 
toad,  can  be  studied  from  live  specimens  in  the  field  or  in  breeding- 
cages  and  aquaria  in  the  laboratory.  The  eggs  of  the  toad  may  be 
found  in  April  and  May  (the  toads  are  heard  trilling  at  egg-laying 
time)  in  ponds.  The  eggs  look  like  the  heads  of  black  pins,  and  are 
in  single  rows  in  long  strings  of  transparent  jelly,  which  are  usually 
wound  around  sticks  or  plant-stems  at  the  bottom  of  the  pond  near 
the  shore.  Bring  some  of  these  strings  into  the  schoolroom  and 
keep  them  in  water  in  shallow  dishes.  Keep  them  in  the  light,  but 
not  in  direct  sunlight.  In  the  dishes  put  some  small  stones  and 
mud  from  the  pond,  arranging  them  in  a  slope,  thus  making  different 
depths  of  water.  Stones  with  green  algae  on  should  be  selected,  for 
algae  are  the  food  of  the  tadpoles.  The  eggs  will  hatch  in  two  or 
three  days,  and  if  too  many  tadpoles  are  not  kept  in  the  dish,  and 
the  little  aquarium  be  well  cared  for,  the  whole  postembryonic  de- 
velopment of  the  toad  can  be  well  observed.  For  the  study  of  the 
development  from  prepared  specimens  the  teacher  should  have  a 
complete  series  of  stages  from  egg  to  adult  toad  in  alcohol.  The 
specimens  may  be  examined  by  the  students  in  connection  with  a 
talk  from  the  teacher  on  the  life-history  of  the  toad. 

If  the  study  is  made  from  prepared  specimens,  make 
drawings  of  egg-strings,  and  of  a  single  egg  magnified 
and  shaded  to  indicate  its  color.  Draw  each  specimen  of 
the  series  of  tadpoles,  noting  in  the  youngest  the  presence 
of  gills  and  tail  and  absence  of  legs  and  eyes;  in  the 

55 


56  ELEMENTARY  ZOOLOGY 

older  the  appearance  of  eyes,  the  shrivelling  of  the  gills, 
shrinking  of  the  tail  and  development  of  legs ;  in  the  still 
older  the  characteristic  shape,  in  miniature,  of  the  adult 
toad. 

In  observing  the  course  of  development  of  the  living 
specimens  there  should  be  made,  in  addition  to  the  draw- 
ings, notes  showing  the  duration  of  the  egg  stage,  and 
the  time  elapsing  between  all  important  changes  (as  seen 
externally)  in  the  body  of  the  young.  Observations  and 
notes  on  the  general  behavior  of  tadpoles  should  also  be 
made ;  note  the  swimming,  the  feeding,  the  gradual  leav- 
ing of  the  water,  etc. 

In  addition  to  the  easily  seen  external  changes  in  the 
body,  very  important  ones  in  the  internal  organs  take 
place  during  development.  Perhaps  the  most  important 
of  these  concerns  the  lungs.  The  young  gilled  toad 
breathes  as  a  fish  does,  but  gradually  its  gills  are  lost, 
while  at  the  same  time  lungs  develop  and  the  tadpole 
comes  to  the  surface  to  breathe  air  like  any  lunged  aquatic 
animal.  The  toad  on  leaving  the  water  changes  its  diet 
from  vegetable  to  animal  food ;  a  tadpole  feeds  on  aquatic 
algae;  a  toad  preys  on  insects.  Correlated  with  the 
change  in  habit,  the  intestine  during  development  under- 
goes some  marked  changes,  becoming  relatively  dimin- 
ished in  length. 

For  an  account  of  the  development  of  the  toad  see 
Gage's  "Life-history  of  a  Toad"  or  Hodge's  "The 
Common  Toad. ' 


CHAPTER    XIII 

MULTIPLICATION  AND  DEVELOPMENT.— MUL- 
TIPLICATION   OF    ONE-CELLED    ANIMALS 

Multiplication. — We  know  that  any  living  animal  has 
parents;  that  is,  has  been  produced  by  other  animals 
which  may  still  be  living  or  be  now  dead  or,  as  with 
Amoeba,  may  have  changed,  by  division,  into  new  indi- 
viduals. Individuals  die,  but  before  death,  they  produce 
other  individuals  like  themselves.  If  they  did  not,  their 
kind  or  species  would  die  with  them.  This  production 
of  new  animals  constantly  going  on  is  called  the  repro- 
duction or  multiplication  of  animals.  The  process  is 
well  called  multiplication,  because  each  female  animal 
normally  produces  more  than  one  new  individual.  She 
may  produce  only  one  at  a  time,  one  a  year,  as  many  of 
the  sea-birds  do  or  as  the  elephant  does,  but  she  lives 
many  years.  Or  she  may  produce  hundreds,  or  thou- 
sands, or  even  millions  of  young  in  a  very  short  time. 
A  lobster  lays  10,000  eggs  at  a  time.  Nearly  nine 
millions  of  eggs  have  been  taken  from  the  body  of  a 
thirty-pound  female  codfish.  As  a  matter  of  fact  but 
very,  very  few  of  these  eggs  produce  new  animals  which 
reach  maturity.  From  the  10,000  eggs  produced  by  the 
lobster  each  year  an  average  of  but  two  new  mature 
lobsters  is  produced.  There  is  always  a  struggle  for  food 
and  for  place  going  on  among  animals,  for  many  more 
are  produced  than  there  are  food  and  room  for,  and  so  of 
all  the  new  or  young  animals  which  are  born  the  great 

57 


5^  ELEMENTARY  ZOOLOGY 

majority  are  killed  before  they  reach  maturity.  In  a  later 
chapter  more  attention  will  be  given  to  this  great  struggle 
for  life. 

In  the  preceding  paragraph  it  has  been  stated  that 
"  we  know  that  any  living  animal  has  parents ;  that  is,  has 
been  produced  by  other  animals  which  may  still  be  living 
or  be  now  dead."  This  is  a  statement,  however,  which 
has  found  complete  acceptance  only  in  modern  times. 
It  is  a  familiar  fact  that  a  new  kitten  comes  into  the  world 
only  through  being  born  ;  that  it  is  the  offspring  of  parents 
of  its  kind.  But  we  may  not  be  personally  familiar  with 
the  fact  that  a  new  starfish  comes  into  the  world  only  as 
the  production  of  parent  starfish,  or  that  a  new  earth- 
worm can  be  produced  only  by  other  earthworms.  But 
naturalists  have  proved  these  statements.  All  life  comes 
from  life ;  all  organisms  are  produced  by  other  organisms. 
And  new  individuals  are  produced  by  other  individuals  of 
the  same  kind.  That  these  statements  are  true  all 
modern  observations  and  investigations  of  the  origin  of 
new  individuals  prove.  But  in  the  days  of  the  earlier 
naturalists  the  life  of  the  microscopic  organisms  like 
Amoeba  and  Paramcecium,  and  even  that  of  many  of  the 
larger  but  unfamiliar  animals,  was  shrouded  in  mystery. 
And  various  and  strange  beliefs  were  held  regarding  the 
origin  of  new  individuals. 

Spontaneous  generation. — The  ancients  believed  that 
many  animals  were  spontaneously  generated.  The  early 
naturalists  thought  that  flies  arose  by  spontaneous  genera- 
tion from  the  decaying  matter  of  dead  animals.  Frogs 
and  many  insects  were  thought  to  be  generated  spontane- 
ously from  mud,  and  horse-hairs  in  water  were  thought 
to  change  into  water-snakes.  But  such  beliefs  were 
easily  shown  to  be  based  on  error,  and  have  been  long 
discarded  by  zoologists.  But  the  belief  that  the  micro- 
scopic organisms,  such  as  bacteria  and  infusoria,  were 


MULTIPLICATION  AND  DEVELOPMENT  59 

spontaneously  generated  in  stagnant  water  or  decaying 
organic  liquids  was  held  by  some  naturalists  until  very 
recent  times.  And  it  was  not  so  easy  to  disprove  the 
assertions  of  such  believers.  If  some  water  in  which 
there  are  apparently  no  living  organisms,  however 
minute,  be  allowed  to  stand  for  a  few  days,  it  will 
come  to  swarm  with  microscopic  plants  and  animals. 
Any  organic  liquid,  as  a  broth  or  a  vegetable  infusion, 
exposed  to  the  air  for  a  short  time  becomes  foul  through 
the  presence  of  innumerable  microsccpic  organisms.  But 
it  has  been  certainly  proved  that  these  organisms  are  not 
spontaneously  produced  in  the  water  or  organic  fluid. 
A  few  of  them  enter  the  water  from  the  air,  in  which  there 
are  always  greater  or  less  numbers  of  spores  of  micro- 
scopic organisms.  These  spores  germinate  quickly  when 
they  fall  into  water  or  some  organic  liquid,  and  the  rapid 
succession  of  generations  soon  gives  rise  to  the  hosts  of 
bacteria  and  one-celled  animals  which  infest  all  standing 
water.  If  all  the  active  organisms  and  inactive  spores  in 
a  glass  of  water  are  killed  by  boiling  the  water,  and  this 
sterilized  water  be  put  into  a  sterilized  glass,  and  this 
glass  be  so  well  closed  that  germs  or  spores  cannot  pass 
from  the  air  without  into  the  sterilized  liquid,  no  living 
animals  will  ever  appear  in  it.  We  know  of  no  instance 
of  the  spontaneous  generation  of  animals,  and  all  the 
animals  whose  life-history  we  know  are  produced  by  other 
animals  of  the  same  kind. 

Simplest  multiplication  and  development. — The  sim- 
plest method  of  multiplication  and  the  simplest  kind  of 
development  shown  among  animals  are  exhibited  by  such 
simple  animals  as  Amccba  and  Paramaccium.  The  pro- 
duction of  new  individuals  is  accomplished  in  Amoeba  by 
a  simple  division  or  fission  of  its  body  (a  single  cell)  into 
two  practical ly  equivalent  parts.  An  Amccba  which  has 
grown  for  some  time  contracts  all  of  its  finger-like 


60  ELEMENTARY  ZOOLOGY 

processes,  the  pseudopodia,  and  its  body  becomes  con- 
stricted. This  constriction  or  fissure  increases  inwards 
so  that  the  body  is  soon  divided  fairly  in  two.  There  are 
now  two  Amceba,  each  half  the  size  of  the  original  one; 
each,  indeed,  actually  one-half  of  the  original  one.  The 
original  Amoeba  was  the  parent;  the  two  halves  of  it  are 
the  young.  Each  of  the  young  possesses  all  of  the  char- 
acteristics and  powers  of  the  parent ;  each  can  move,  eat, 
feel,  "grow,  and  reproduce  by  fission.  The  only  change 
necessary  for  the  young  or  new  Avt&b'a  to  become  like  its 
parent,  is  that  of  simple  growth  to  a  size  about  twice  its 
present  size.  The  development  here  is  reduced  to  a 
minimum.  Just  as  the  simplest  animals  perform  the  other 
life-processes,  such  as  taking  and  digesting  food,  breath- 
ing and  feeling,  in  an  extremely  primitive  simple  way,  so 
do  they  perform  the  necessary  life-process  of  reproduction 
or  multiplication  in  the  simplest  way  shown  among 
animals. 

In  the  case  of  Paramcecium  the  process  of  multiplication 
is  slightly  more  complex  than  that  of  Amoeba  in  the  fact 
that  sometimes  before  the  simple  fission  of  the  body  takes 
place  the  interesting  phenomenon  of  conjugation  occurs. 
Paramoecium  may  reproduce  itself  for  many  generations 
by  simple  fission,  but  a  generation  finally  appears  in  which 
conjugation  takes  place.  Two  individuals  come  together 
and  each  exchanges  with  the  other  a  part  of  its  nucleus. 
Then  the  two  individuals  separate  and  each  divides  into 
two.  The  result  of  the  conjugation,  or  the  coming 
together,  of  two  individuals  with  mutual  interchange  of 
nuclear  substance  is  to  give  to  the  new  Paramoecia  pro- 
duced by  the  conjugating  individuals  a  body  which 
contains  part  of  the  body-substance  of  two  distinct  indi- 
viduals. If  the  two  conjugating  individuals  differ  at  all — 
and  they  always  do  differ,  because  no  two  individual 
animals,  although  belonging  to  the  same  species,  are 


MULTIPLICATION  AND  DEVELOPMENT  61 

exactly  alike — the  new  individual,  made  up  of  parts  of 
each  of  them,  will  differ  slightly  from  both.  Nature 
seems  intent  on  making  every  new  individual  differ  slightly 
from  the  individual  which  precedes  it.  And  the  method 
of  multiplication  which  Nature  has  adopted  to  produce 
the  result  is  the  method  which  we  have  seen  exhibited  in 
its  simplest  form  in  the  case  of  Paramcechnn — the  method 
of  having  two  individuals  take  part  in  the  production  of 
a  new  one. 

The  development  of  the  new  Paramoccia  is  a  little  more 
complex  than  that  of  Amccba.  Not  only  must  the  new 
Paramccciinn  grow  to  the  size  of  the  original  one,  but  it 
must  develop  those  slight,  but  apparent,  modifications  of 
the  parts  of  its  body  which  we  can  recognize  in  the  full- 
grown,  fully  developed  Parainoccium  individual.  A  new 
mouth-opening  must  develop  on  the  new  individual 
formed  of  the  hinder  half  of  the  original  Paramccchuu  and 
new  cilia  must  be  developed.  Thus  there  is  a  slight 
advance  in  complexity  of  development,  just  as  there  is  in 
complexity  of  structure  in  Paramachnn  as  compared  with 
Amccba.  In  the  many-celled  animals  this  complexity  of 
development  is  carried  to  an  extreme. 

Birth  and  hatching. — When  a  young  animal  is  born 
alive,  it  usually  resembles  in  appearance  and  structure  the 
parent,  although  of  course  it  is  much  smaller,  and  requires 
always  a  certain  time  to  complete  its  development  and 
become  mature.  A  young  kangaroo  or  opossum  is 
carried  for  some  time  after  its  birth  in  an  external  pouch 
on  the  mother's  body  and  is  a  very  helpless  animal.  A 
young  kitten  is  born  with  eyes  not  yet  opened  and  must 
be  fed  by  the  mother  for  several  weeks.  On  the  other 
hand  young  Rocky  Mountain  sheep  are  able  to  run  about 
swiftly  within  a  few  hours  after  birth. 


62  ELEMENTARY  ZOOLOGY 

Most  animals  appear  first  as  eggs  laid  by  the  mother. 
This  is  true  of  the  birds,  the  reptiles,  the  fishes,  the 
insects,  and  most  of  the  hosts  of  invertebrate  animals, 
This  egg  may  be  cared  for  by  the  parent  as  with  the 
birds,  or  simply  deposited  in  a  safe  place  as  with  most 
insects,  or  perhaps  dropped  without  care  into  the  water  as 
with  most  marine  invertebrates.  The  young  animal  which 
issues  from  the  egg  may  at  the  time  of  its  hatching 
resemble  the  parent  in  appearance  and  structural  character 
(although  always  much  smaller)  as  with  the  birds,  some 
of  the  insects,  and  many  of  the  other  animals.  Or  it  may 
issue  in  a  so-called  larval  condition,  in  which  it  resembles 
the  parent  but  slightly  or  not  at  all,  as  is  the  case  with 
the  gill-bearing,  legless,  tailed  tadpole  of  the  frog  or  the 
crawling,  wingless,  wormlike  caterpillar  of  the  butterfly, 
or  the  maggot  of  the  house-fly. 

Life-history. — Any  animal  which  hatches  from  an  egg 
has  undergone  a  longer  or  shorter  period  of  development 
within  the  egg-shell  before  hatching.  The  development 
of  an  animal  from  first  germ-cell  to  the  time  it  leaves  the 
egg,  for  example,  the  development  of  the  embryo  chick 
from  the  first  cell  to  time  of  hatching,  is  called  its  em- 
bryonic development;  and  the  development  from  then  on, 
for  example,  that  of  the  chick  to  adult  hen  or  rooster, 
or  that  of  tadpole  to  frog,  is  called  the  post-embryonic 
development.  Beginning  students  of  animals  cannot 
study  the  embryonic  development  (embryology}  of  animals 
readily,  but  they  can  in  many  cases  easily  follow  the 
course  of  the  post-embryonic  development,  and  this  stud}' 
will  always  be  interesting  and  valuable,  When  the 
"  life-history  "  of  an  animal  is  spoken  of  in  this  book,  or 
other  elementary  text-book  of  zoology,  it  is  the  history 
of  the  life  of  the  animal  from  the  time  of  its  birth  or 
hatching  to  and  through  adult  condition  that  is  meant, 
not  the  complete  life-history  from  beginning  single  egg- 


MULTIPLICATION  AND  DEVELOPMENT  63 

cell  to  the  end.  In  all  of  the  study  of  the  different  kinds 
of  animals  to  which  the  rest  of  this  book  is  devoted, 
attention  will  be  paid  to  their  life-history. 


PART  II 
SYSTEMATIC  ZOOLOGY 

CHAPTER    XIV 
THE    CLASSIFICATION    OF   ANIMALS 

Basis  and  significance  of  classification. — It  is  the 
common  knowledge  of  all  of  us  that  animals  are  classified: 
that  is,  that  the  different  kinds  are  arranged  in  the  mind 
of  the  zoologist  and  in  the  books  of  natural  history,  in 
various  groups,  and  that  these  various  groups  are  of 
different  rank  or  degree  of  comprehensiveness.  A  group 
of  high  rank  or  great  comprehensiveness  includes  groups 
of  lower  rank,  and  each  of  these  includes  groups  of  still 
lower  rank,  and  so  on,  for  several  degrees.  For  example, 
we  have  already  learned  that  the  toad  belongs  to  the 
great  group  of  back-boned  animals,  the  Vertebrates,  as 
the  group  is  called.  So  do  the  fishes  and  the  birds,  the 
reptiles  and  the  mammals  or  quadrupeds.  But  each  of 
these  constitutes  a  lesser  group,  and  each  may  in  turn  be 
subdivided  into  still  lesser  groups. 

In  the  early  days  of  the  study  of  animals  and  plants 
their  classification  or  division  into  groups  was  based  on 
the  resemblances  and  the  differences  which  the  early 
naturalists  found  among  the  organisms  they  knew.  At 
first  all  of  the  classifying  was  done  by  paying  attention 
to  external  resemblances  and  differences,  but  later  when 
naturalists  began  to  dissect  animals  and  to  get  acquainted 

65 


66  ELEMENTARY  ZOOLOGY 

with  the  structure  of  the  whole  body,  the  differences  and 
likenesses  of  inner  parts,  such  as  the  skeleton  and  the 
organs  of  circulation  and  respiration,  were  taken  into  ac- 
count. At  the  present  time  and  ever  since  the  theory  of 
descent  began  to  be  accepted  by  naturalists  (and  there  is 
practically  no  one  who  does  not  now  accept  it),  the  classifi- 
cation of  animals,  while  still  largely  based  on  resemblances 
and  differences  among  them,  tells  more  than  the  simple 
fact  that  animals  of  the  same  group  resemble  each  other 
in  certain  structural  characters.  It  means  that  the  mem- 
bers of  a  group  are  related  to  each  other  by  descent,  that 
is,  genealogically.  They  are  all  the  descendants  of  a 
common  ancestor ;  they  are  all  sprung  from  a  common 
stock.  And  this  added  meaning  of  classification  explains 
the  older  meaning ;  it  explains  why  the  animals  are  alike. 
The  members  of  a  group  resemble  each  other  in  structure 
because  they  are  actually  blood  relations.  But  as  their 
common  ancestor  lived  ages  ago,  we  can  learn  the  history 
of  this  descent,  and  find  out  these  blood  relationships 
among  animals  only  by  the  study  of  forms  existing  now, 
or  through  the  fragmentary  remains  of  extinct  animals 
preserved  in  the  rocks  as  fossils.  As  a  matter  of  fact 
we  usually  learn  of  the  existence  of  this  actual  blood- 
relationship,  or  the  fact  of  common  ancestry  among 
animals,  by  studying  their  structure  and  finding  out  the 
resemblances  and  differences  among  them.  If  much  alike 
we  believe  them  closely  related;  if  less  alike  we  believe 
them  less  closely  related,  and  so  on.  So  after  all,  though 
the  present-day  classification  means  something  more, 
means  a  great  deal  more,  in  fact,  than  the  classification 
of  the  earlier  naturalists  means,  it  is  largely  based  on 
and  determined  by  resemblances  and  differences  just  as 
was  the  old  classification.  Sometimes  the  fossil  remains 
of  ancient  animals  tell  us  much  about  the  ancestry  and 
descent  of  existing  forms.  For  example,  the  present-day 


THE    CLASSIFICATION  OF  ANIMALS  67 

one-toed  horse  has  been  clearly  shown  by  series  of  fossils 
to  be  descended  from  a  small  five-toed  horse-like  animal 
which  lived  in  the  Tertiary  age. 

Importance  of  development  in  determining  classifica- 
tion.— A  very  important  means  of  determining  the 
relationships  among  animals  is  by  studying  their  develop- 
ment. If  two  kinds  of  animals  undergo  very  similar 
development,  that  is,  if  in  their  development  and  growth 
from  egg-cell  to  adult  they  pass  through  similar  stages, 
they  are  nearly  related.  And  by  the  correspondence  or 
lack  of  correspondence,  by  the  similarity  or  dissimilarity 
of  the  course  of  development  of  different  animals  much 
regarding  their  relationship  to  each  other  is  revealed. 
Sometimes  two  kinds  of  animals  which  are  really  nearly 
related  come  to  differ  very  much  in  appearance  in  their 
fully  developed  adult  condition  because  of  the  widely  differ- 
ent life-habits  the  two  may  have.  But  if  they  are  nearly 
related  their  developmental  stages  will  be  closely  similar 
until  the  animals  are  almost  fully  developed.  For  exam- 
ple, certain  animals  belonging  to  the  group  which  includes 
the  crabs,  lobsters,  and  crayfishes,  have  adopted  a  para- 
sitic habit  of  life,  and  in  their  adult  condition  live  attached 
to  the  bodies  of  certain  kinds  of  true  crabs.  As  these 
parasites  have  no  need  of  moving  about,  being  carried  by 
their  hosts,  they  have  lost  their  legs  by  degeneration,  and 
the  body  has  come  to  be  a  mere  sac-like  pulsating  mass, 
attached  to  the  host  by  slender  root-like  processes,  and 
not  resembling  at  all  the  bodies  of  their  relatives  the 
crabs  and  crayfishes.  If  we  had  to  trust,  in  making  out 
our  classification,  solely  to  structural  resemblances  and 
differences,  we  should  never  classify  the  Sacculina  (the 
parasite)  in  the  group  Crustacea,  which  is  the  group  in- 
cluding the  crabs  and  lobsters  and  crayfishes.  But  the 
young  Sacculina  is  an  active  free-swimming  creature 
resembling  the  young  crabs  and  young  shrimps.  By  a 


68  ELEMENTARY  ZOOLOGY 

study  of  the  development  of  Sacculina  we  find  that  it  is 
more  closely  related  to  the  crabs  and  crayfishes  and  the 
other  Crustaceans  than  to  any  other  animals,  although  in 
adult  condition  it  does  not  at  all,  at  least  in  external  ap- 
pearance, resemble  a  crab  or  lobster. 

Scientific  names. — To  classify  animals  then,  is  to  deter- 
mine their  true  relationships  and  to  express  these  relation-- 
ships by  a  scheme  of  groups.  To  these  groups  proper 
names  are  given  for  convenience  in  referring  to  them. 
These  proper  names  are  all  Latin  or  Greek,  simply 
because  these  classic  languages  are  taught  in  the  schools 
and  colleges  of  almost  all  the  countries  in  the  world,  and 
are  thus  intelligible  to  naturalists  of  all  nationalities.  In 
the  older  days,  indeed,  all  the  scientific  books,  the 
descriptions  and  accounts  of  animals  and  plants,  were 
written  in  Latin,  and  now  most  of  the  technical 
words  used  in  naming  the  parts  of  animals  and 
plants  are  Latin.  So  that  Latin  may  be  called  the 
language  of  science.  For  most  of  the  groups  of  animals 
we  have  English  names  as  well  as  Greek  or  Latin  ones 
and  when  talking  with  an  English-speaking  person  we 
can  use  these  names.  But  when  scientific  men  write  of 
animals  they  use  the  names  which  have  been  agreed  on 
by  naturalists  of  all  nationalities  and  which  are  understood 
by  all  of  these  naturalists.  These  Latin  and  Greek 
names  of  animals  laughed  at  by  non-scientific  persons  as 
"jaw-breakers,"  are  really  a  great  convenience,  and  save 
much  circumlocution  and  misunderstanding. 

AN    EXAMPLE    OF   CLASSIFICATION. 

TECHNICAL  NOTE. — There  should  be  provided  a  small  set  of  bird- 
skins  which  will  serve  just  as  well  as  freshly  killed  birds, and  which 
may  be  used  for  successive  classes,  thus  doing  away  with  the  neces- 
sity ot  shooting  birds.  The  birds  suggested  for  use  are  among  the 
commonest  and  most  easily  recognizable  and  obtainable.  They  may 
be  found  in  any  locality  at  any  time  of  the  year.  The  skins  can 


THE  CLASSIFICATION  OF  ANIMALS  69 

he  made  by  some  boy  interested  in  birds  and  acquainted  with 
making  skins,  or  by  the  teacher,  or  can  be  purchased  from  a  natur- 
alists' supply  store,  or  dealer  in  bird  skins.  The  skins  will  cost 
about  25  cents  each.  This  example  or  lesson  in  classification  can 
be  given  just  as  well  of  course  with  other  species  of  birds,  or  with 
a  set  of  some  other  kinds  of  animals,  if  the  teacher  prefers.  Insects 
are  especially  available,  butterflies  perhaps  offering  the  most  readily 
appreciated  resemblances  and  differences. 

Species. — Examine  specimens  of  two  male  downy 
woodpeckers  (the  males  have  a  scarlet  band  on  the  back 
of  the  head).  (In  the  western  States  uses  Gardiner's 
downy  woodpecker.)  Note  that  the  two  birds  are  of  the 
same  size,  have  the  same  colors  and  markings,  and  are 
in  all  respects  alike.  They  are  of  the  same  kind;  simply 
two  individuals  of  the  same  kind  of  animal.  There  are 
hosts  of  other  individuals  of  this  kind  of  bird,  all  alike. 
This  one  kind  of  animal  is  called  a  species.  The  species 
is  the  smallest  *  group  recognized  among  animals.  No  at- 
tempt is  made  to  distinguish  among  the  different  individuals 
of  one  kind  or  species  of  animal  as  we  do  in  our  own  case. 

Examine  a  specimen  of  the  female  downy  wood- 
pecker. It  is  like  the  male  except  that  it  does  not  have 
the  scarlet  neck-band.  But  despite  this  difference  we 
know  that  it  belongs  to  the  same  species  as  the  male 
downy  because  they  mate  together  and  produce  young 
woodpeckers,  male  and  female,  like  themselves.  There 
are  thus  two  sorts  of  individuals, t  male  and  female,  com- 
prised in  each  species  of  animal.  A  species  is  a  group  of 
animals  comprising  similar  individuals  which  produce 
new  individuals  of  the  same  kind  usually  after  the  mating 
together  of  individuals  of  two  sexes  which  may  differ 
somewhat  in  appearance  and  structure. 

*  The  lesser  group  called  variety,  or  subspecies,  we  may  leave  out  of 
consideration  for  the  present. 

\  Some  species  of  animals  are  not  represented  by  male  individuals  ;  and 
in  some  all  the  individuals  are  hermaphrodites,  as  explained  in  chapter 
XIV, 


70  ELEMENTARY  ZOOLOGY 

Examine  a  male  hairy  woodpecker  and  a  female ;  (in 
western  States  substitute  a  Harris's  hairy  woodpecker). 
Note  the  similarity  in  markings  and  structure  to  the 
downy.  Note  the  marked  difference  in  size.  Make  notes 
of  measurements,  colors  and  markings,  and  drawings  of 
bill  and  feet,  showing  the  resemblances  and  the  differ- 
ences between  the  downy  woodpecker  and  the  hairy 
woodpecker.  These  two  kinds  of  woodpeckers  are  very 
much  alike,  but  the  hairy  woodpeckers  are  always  much 
larger  (nearly  a  half)  than  the  downy  woodpeckers  and 
the  two  kinds  never  mate  together.  The  hairy  wood- 
peckers constitute  another  species  of  bird. 

Genus. — Examine  now  a  flicker  (the  yellow-shafted 
or  golden-winged  flicker  in  the  East,  the  red-shafted 
flicker  in  the  West).  Compare  it  with  the  downy  wood- 
pecker and  the  hairy  woodpecker.  Make  notes  referring 
to  the  differences,  also  the  resemblances.  The  flicker 
is  very  differently  marked  and  colored  and  is  also  much 
larger  than  the  downy  woodpecker,  but  its  bill  and  feet 
and  general  make-up  are  similar  and  it  is  obviously  a 
'  *  woodpecker. ' '  It  is,  however,  evidently  another  species 
of  woodpecker,  and  a  species  which  differs  from  either  the 
downy  or  the  hairy  woodpecker  much  more  than  these 
two  species  differ  from  each  other.  There  are  two  other 
species  of  flickers  in  North  America  which,  although 
different  from  the  yellow-shafted  flicker,  yet  resemble  it 
much  more  than  they  do  the  downy  and  hairy  wood- 
peckers or  any  other  woodpeckers.  We  can  obviously 
make  two  groups  of  our  woodpeckers  so  far  studied, 
putting  the  downy  and  hairy  woodpeckers  (together  with 
half  a  dozen  other  species  very  much  like  them)  into  one 
group  and  the  three  flickers  together  into  another  group. 
Each  of  these  groups  is  called  a  germs,  and  genus  is  thus 
the  name  of  the  next  group  above  the  species.  A  genus 
usually  includes  several,  or  if  there  be  such,  many, 


THE  CLASSIFICATION  OF  ANIMALS  71 

similar  species.  Sometimes  it  includes  but  a  single  known 
species.  That  is,  a  species  may  not  have  any  other 
species  resembling  it  sufficiently  to  group  with  it,  and  so 
it  constitutes  a  genus  by  itself.  If  later  naturalists  should 
find  other  species  resembling  it  they  would  put  these  new 
species  into  the  genus  with  the  solitary  species.  Each 
genus  of  animals  is  given  a  Greek  or  Latin  name,  of  a 
single  word.  Thus  the  genus  including  the  hairy  and 
downy  woodpeckers  is  called  Dryobates;  and  the  genus 
including  the  flickers  is  called  Colaptes.  But  it  is  neces- 
sary to  distinguish  the  various  species  which  compose  the 
genus  Colaptes,  and  so  each  species  is  given  a  name  which 
is  composed  of  two  words,  first  the  word  which  is  the 
name  of  the  genus  to  which  it  belongs,  and,  second,  a 
word  which  may  be  called  the  species  word.  The  species 
word  of  the  Yellow-shafted  Flicker  is  auratus  (the  Latin 
word  for  golden),  so  that  its  scientific  name  is  Colaptes 
auratus.  The  natural  question.  Why  not  have  a  single 
word  for  the  name  of  each  species  ?  may  be  answered  thus : 
There  are  already  known  more  than  500,000  distinct 
species  of  living  animals ;  it  is  certain  that  there  are  no 
less  than  several  millions  of  species  of  living  animals; 
new  species  are  being  found,  described  and  named  con- 
stantly; with  all  the  possible  ingenuity  of  the  word- 
makers  it  would  be  an  extremely  difficult  task  to  find  or 
to  build  up  enough  words  to  give  each  of  these  species  a 
separate  name.  This  is  not  attempted.  The  same 
species  word  is  often  used  for  several  different  species  of 
animals,  but  never  for  more  than  one  species  belonging 
to  a  given  genus.  And  the  names  of  the  genera  are 
never  duplicated.  (There  are,  of  course,  much  fewer 
genera  than  species,  and  the  difficulty  of  finding  words 
for  them  is  not  so  serious.)  Thus  the  genus  word  in  the 
two-word  name  of  a  species  indicates  at  once  to  just  what 
particular  genus  in  the  whole  animal  kingdom  the  species 


72  ELEMENTARY  ZOOLOGY 

belongs,  while  the  second  or  species  word  distinguishes  it 
from  the  few  or  many  other  species  which  are  included  in  the 
same  genus.  This  manner  of  naming  species  of  animals 
and  plants  (for  plants  are  given  their  scientific  names 
according  to  the  same  plan)  was  devised  by  the  great 
Swedish  naturalist  Linnaeus  in  the  middle  of  the 
eighteenth  century  and  has  been  in  use  ever  since. 

Family. — Examine  a  red-headed  woodpecker  (J^lela- 
nerpes  crytJirocepJialus)  and  a  sapsucker  (Spliyrapicus 
varius)  and  any  other  kinds  of  woodpeckers  which  can  be 
got.  Find  out  in  what  ways  the  hairy  and  downy 
woodpeckers  (genus  Dry  ob  cites),  the  flickers  (genus 
Colapies)  and  the  other  woodpeckers  resemble  each  other. 
Examine  especially  the  bill,  feet,  wings  and  tail.  These 
birds  differ  in  size,  color  and  markings,  but  they  are 
obviously  all  alike  in  certain  important  structural  respects. 
We  recognize  them  all  as  woodpeckers.  We  can  group 
all  the  woodpeckers  together,  including  several  different 
genera,  to  form  a  group  which  is  called  a  family.  A 
family  is  a  group  of  genera  which  have  a  considerable 
number  of  common  structural  features.  Each  family  is 
given  a  proper  name  consisting  of  a  single  word.  The 
family  of  woodpeckers  is  named  Picidce. 

We  have  already  learned  that  resemblances  between 
animals  indicate  (usually)  relationship,  and  that  classify- 
ing animals  is  simply  expressing  or  indicating  these 
relationships.  When  we  group  several  species  together 
to  form  a  genus  we  indicate  that  these  species  are  closely 
related.  And  similarly  a  family  is  a  group  of  related 
genera. 

Order. — There  are  other  groups*  higher  or  more  com- 

*Each  of  these  higher  groups  has  a  proper  name  composed  of  a  single 
word.  In  the  case  of  no  group  except  the  species  is  a  name-word  ever 
duplicated.  Each  genus,  family,  order,  or  higher  group  has  a  name-word 
peculiar  to  it,  and  belonging  to  it  alone. 


THE  CLASSIFICATION  OF  ANIMALS  73 

prehensive  than  families,  but  the  principle  on  which  they 
are  constituted  is  exactly  the  same  as  that  already 
explained.  Thus  a  number  of  related  families  are  grouped 
together  to  form  an  order.  All  the  fowl-like  birds,  in- 
cluding the  families  of  pheasants,  turkeys,  grouse  and 
quail,  all  obviously  related,  constitute  the  order  of  gal- 
linaceous birds  called  Gallince.  The  families  of  vultures, 
hawks  and  owls  constitute  the  order  of  birds  of  prey, 
the  Raptores,  and  the  families  of  the  thrushes,  wrens, 
warblers,  sparrows,  black-birds,  and  many  others  con- 
stitute the  great  order  of  perching  birds  (including  all  the 
singing  birds)  called  the  Passeres. 

Class  and  branch. — But  it  is  evident  that  all  of  these 
orders,  together  with  the  other  bird  orders,  ought  to  be 
combined  into  a  great  group,  which  shall  include  all  the 
birds,  as  distinguished  from  all  other  animals,  as  the 
fishes,  insects,  etc.  Such  a  group  of  related  orders  is 
called  a  class.  The  class  of  birds  is  named  Aves.  There 
is  a  class  of  fishes,  Pisces,  and  one  of  frogs  and  salaman- 
ders, Batrachia,  one  of  snakes  and  lizards  called  Reptilia, 
and  one  of  the  quadrupeds  which  give  milk  to  their  young 
called  Mammalia.  Each  of  these  classes  is  composed  of 
several  orders,  each  of  which  includes  several  families  and 
so  on  down.  But  these  five  classes  of  Pisces,  Batrachia, 
Reptilia,  Aves  and  Mammals  agree  in  being  composed  of 
animals  which  have  a  backbone  or  a  backbone-like  struc- 
ture, while  there  are  many  other  animals  which  do  not 
have  a  backbone,  such  as  the  insects,  the  starfishes,  etc. 
Hence  these  five  backboned  classes  may  be  brought 
together  into  a  higher  group  called  a  branch  or  phylum. 
They  compose  the  branch  of  backboned  animals,  the 
branch  Vertebrata;  all  the  animals  like  the  starfishes, 
sea-urchins  and  sea-lilies  which  have  the  parts  of  their 
body  arranged  in  a  radiate  manner  compose  the  branch 
Echinodermata;  all  the  animals  like  the  insects  and 


74  ELEMENTARY  ZOOLOGY 

spiders  and  centipedes  and  crabs  and  crayfishes  which 
have  the  body  composed  of  a  series  of  segments  or  rings 
and  have  legs  or  appendages  each  composed  of  a  series 
of  joints  or  segments  make  up  the  branch  Arthropoda. 
And  so  might  be  enumerated  all  the  great  branches  or 
principal  groups  into  which  the  animal  kingdom  is  divided. 
In  the  remainder  of  this  book  the  classification  of 
animals  is  always  kept  in  sight,  and  the  student  will  see 
the  terms  species,  genus,  family,  order,  etc.,  practically 
used.  In  it  all  should  be  kept  constantly  in  mind  the 
significance  of  classification,  that  is,  the  existence  of  actual 
relationships  among  animals  through  descent. 


CHAPTER   XV 

BRANCH    PROTOZOA:    THE    ONE-CELLED 
ANIMALS 

Of  this  group  the  structure  and  life-history  of  the 
Amoeba  (Amceba  sp.)  and  the  Slipper  Animalcule  (Para- 
mcecium  sp.)  have  already  been  treated  in  Chapter  VI. 
Another  example  is  the 

BELL    ANIMALCULE  •  Vorticella  sp.) 

TECHNICAL  NOTE. — Specimens  of  Vorticella  may  usually  be 
found  in  the  same  water  with  Amceba  and  Paramcecium.  The 
individuals  live  together  in  colonies,  a  single  colony  appearing  to 
the  naked  eye  as  a  tiny  whitish  mould-like  tuft  or  spot  on  the 
surface  of  some  leaf  or  stem  or  root  in  the  water.  Touch  such  a 
spot  with  a  needle,  and  if  it  is  a  Vorticellid  colony  it  will  contract 
instantly.  Bring  bits  of  leaves,  stems,  etc.,  bearing  Vorticellid 
colonies  into  the  laboratory  and  keep  in  a  small  stagnant-water 
aquarium  (a  battery-jar  of  pond-water  will  do). 

Examine  a  colony  of  Vorticella  in  a  watch-glass  of 
water  or  in  a  drop  of  water  on  a  glass  slide  under  the 
microscope.  Note  the  stemmed  bell-shaped  bodies 
which  compose  the  colony.  Each  bell  and  stem  together 
form  an  individual  Vorticella  (fig.  8.)  How  are  the 
members  of  the  colony  fastened  together  ?  Tap  the  slide 
and  note  the  sudden  contraction  of  the  animals ;  also  the 
details  of  contraction  in  the  case  of  an  individual.  Watch 
the  colony  expand ;  note  the  details  of  this  movement  in 
the  case  of  an  individual. 

Make  drawings  showing  the  colony  expanded  and  con- 
tracted. 

With  higher  power  examine  a  single  individual.  Note 

75 


76 


ELEMENTARY  ZOOLOGY 


the  thickened,  bent-out,  upper  margin  of  the  bell.  This 
margin  is  called  the  peristome.  With 
what  is  it  fringed  ?  The  free  end  of  the 
bell  is  nearly  filled  by  a  central  disk, 
the  epistome,  with  arched  upper  surface 
and  a  circlet  of  cilia.  Between  the 
epistome  and  peristome  is  a  groove, 
the  mouth  or  vestibule,  which  leads 
into  the  body.  Study  the  internal 
structure  of  the  transparent,  bell- 
shaped  body.  Note  the  differentia- 
tion of  the  protoplasm  comprising  the 
body  into  an  inner  transparent  color- 
less endosarc  containing  various  dark- 
colored  granules,  vacuoles,  oil-drops, 
etc.,  and  an  outer  uniformly  granular 
ectosarc  not  containing  vacuoles.  Is 
the  stalk  formed  of  ectosarc  or  en- 
dosarc or  of  both  ?  Note  the  curved 
nucleus  lying  in  the  endosarc.  (This 
may  be  difficult  to  distinguish  in  some 
specimens.)  Note  the  numerous  large 

FIG.  *.—  Vorticelia  sp. ;  circular  granules,  the  food  vacuoles. 
one  individual  with  Note  the  contractile  vesicle,  larger  and 

stalk   coiled,   and    one  ,  .  A, 

with    stalk   extended,  clearer  than  the  food  vacuoles.      Note 
(From  life.)  ^e  thin  cuticle  lining  the  whole  body 

externally.       A  high  magnification  will  show  fine  trans- 
verse ridges  or  rows  of  dots  on  the  cuticle. 

Make  a  drawing  showing  the  internal  structure. 
Observe  a  living  specimen  carefully  for  some  time  to 
determine  all  of  its  movements.  Note  the  contraction 
and  extension  of  the  stalk,  the  movements  of  the  cilia  of 
peristome  and  epistome,  the  flowing  or  streaming  of  the 
fluid  endosarc  (indicated  by  the  movements  of  the  food 
vacuoles),  the  behavior  of  the  contractile  vesicle. 


BRANCH  PROTOZOA:   THE   ONE-CELLED  ANIMALS       77 

Make  notes  and  drawings  explaining  these  motions. 

Specimens  of  Vorticclla  may  perhaps  be  found  dividing, 
or  two  bell-shaped  bodies  may  be  found  on  a  single  stem, 
one  of  the  bodies  being  sometimes  smaller  than  the  other. 
These  two  bodies  have  been  produced  by  the  longitudinal 
division  or  fission  of  a  single  body.  In  this  process  a 
cleft  first  appears  at  the  distal  end  of  the  bell-shaped 
body,  and  gradually  deepens  until  the  original  body  is 
divided  quite  in  two.  The  stalk  divides  for  a  very  short 
distance.  One  of  the  new  bell-shaped  bodies  develops  a 
circlet  of  cilia  near  the  stalked  end.  After  a  while  it 
breaks  away  and  swims  about  by  means  of  this  basal 
circlet  of  cilia.  Later  it  settles  down,  becomes  attached 
by  its  basal  end,  loses  its  basal  cilia  and  develops  a  stalk. 

4 '  Conjugation  occurs  sometimes,  but  it  is  unlike  the 
conjugation  of  Paramcceium  in  two  important  points: 
Firstly,  the  conjugation  is  between  two  dissimilar  forms ; 
an  ordinary  large-stalked  form,  and  a  much  smaller  free- 
swimming  form  which  has  originated  by  repeated  division 
of  a  large  form.  Secondly,  the  union  of  the  two  is  a 
complete  and  permanent  fusion,  the  smaller  being 
absorbed  into  the  larger.  This  permanent  fusion  of  a 
small  active  cell  with  a  relatively  large  fixed  cell,  followed 
by  division  of  the  fused  mass,  presents  a  striking  analogy 
to  the  process  of  sexual  reproduction  occurring  in  higher 
animals. ' 


OTHER    PROTOZOA 

Besides  the  Amoeba^  Paratncecium^  and  Vorticella  there 
are  thousands  of  other  Protozoa.  Most  of  them  live  in 
water,  but  a  few  live  in  damp  sand  or  moss,  and  some 
live  inside  the  bodies  of  other  animals  as  parasites.  Of 
those  which  live  in  water  some  are  marine,  while  others 
are  found  only  in  fresh-water  streams  and  lakes. 


7$  ELEMENTARY  ZOOLOGY 

Form  of  body. — The  Protozoa  all  agree  in  having  the 
body  composed  for  its  whole  lifetime  of  a  single  cell,* 
but  they  differ  much  in  shape  and  appearance.  Some  of 
them  are  of  the  general  shape  and  character  of  Amoeba, 
sending  out  and  retracting  blunt,  finger-like  pseudopodia, 
the  body-mass  itself  having  no  fixed  form  or  outline  but 


FIG.  9.  — Sun  animalcule,  a  fresh-water  protozoan  with  a  siliceous  skeleton, 
and  long  thread-like  protoplasmic  prolongations.     (From  life.) 

constantly  changing.  Others  have  the  body  of  definite 
form,  spherical,  elliptical,  or  flattened,  enclosed  by  a  thin 
cuticle,  and  having  a  definite  number  of  fine  thread-like 
or  hair-like  protoplasmic  prolongations  called  flagella  or 

*  In  some  Protozoa  a  number  of  similar  cells  temporarily  unite  to  form  a 
colony,  but  each  cell  may  still  be  regarded  as  an  individual  animal. 


BRANCH  PROTOZOA:   THE  ONE-CELLED  ANIMALS       79 


cilia.  Many  of  the  familiar  Protozoa  of  the  fresh-water 
ponds  always  have  two  whiplash-like  flagella  projecting 
from  one  end  of  the  body.  By  means  of  the  lashing  of 
these  flagella  in  the  water  the  tiny  creature  swims  about. 
Others  have  many  hundreds  of  fine  short  cilia  scattered, 
sometimes  in  regular  rows,  over  the  body-surface.  The 
Protozoan  swims  by  the  vibration  of  these  cilia  in  the 
water. 

There  is  no  stagnant  pool,  no  water  standing  exposed 
in  watering-trough  or  bar- 
rel which  does  not  contain 
thousands  of  individuals  of 
the  one-celled  animals. 
And  in  any  such  stagnant 
water  there  may  always  be 
found  several  or  many  dif- 
ferent kinds  or  species.  A 
drop  of  this  water  examined 
with  the  compound  micro- 
. scope  will  prove  to  be  a 
tiny  world  (all  an  ocean) 
with  most  of  its  animals  and 
plants  one-celled  in  struc- 
ture. A  few  many-celled 
animals  will  be  found  in  it 
preying  on  the  one-celled 
ones.  There  are  sudden 
and  violent  deaths  here,  and 
births  (by  fission  of  the 
parent)  and  active  locomo- 
tion and  food-getting  and 
growth  and  all  of  the  busi- 
nesses and  functions  of  life 
which  we  are  accustomed 
world  of  larger  animals. 


which  has  the  nucleus  in  the  shai 
of  a   string   or   chain    of  bead- 


FIG.  10.  —  Stcntor  sp. ;  a  protozoan 
which  may  be  fixed,  like  Vortifellu, 
or  free-swimming,  at  will,  and 

hape 
-like 

bodies.  The  figure  shows  a  single 
individual  as  it  appeared  when  fixed, 
with  elongate,  stalked  bodv,  and  as 
it  appeared  when  swimming  about, 
with  contracted  body.  (From  life.) 

to  see   in   the   more   familiar 


So  ELEMENTARY  ZOOLOGY 

Marine  Protozoa. — One  usually  thinks  of  the  ocean  as 
the  home  of  the  whales  and  the  seals  and  the  sea-lions,  and 
of  the  countless  fishes,  the  cod,  and  the  herring,  and  the 
mackerel.  Those  who  have  been  on  the  seashore  will 
recall  the  sea-urchins  and  starfishes  and  the  sea-anemones 
which  live  in  the  tide-pools.  On  the  beach  there  are  the 
innumerable  shells,  too,  each  representing  an  animal 
which  has  lived  in  the  ocean.  But  more  abundant  than 
all  of  these,  and  in  one  way  more  important  than  all, 
are  the  myriads  of  the  marine  Protozoa. 

Although  the  water  at  the  surface  of  the  ocean  appears 
clear  and  on  superficial  examination  seems  to  contain  no 
animals,  yet  in  certain  parts  of  the  ocean  (especially  in 
the  southern  seas)  a  microscopical  examination  of  this 
water  shows  it  to  be  swarming  with  Protozoa.  And  not 
only  is  the  water  just  at  the  surface  inhabited  by  one- 
celled  animals,  but  they  can  be  found  in  all  the  water  from 
the  surface  to  a  great  depth  below  it.  In  a  pint  of  this 
ocean-water  there  may  be  millions  of  these  minute 
animals.  In  the  oceans  of  the  world  the  number  of  them 
is  inconceivable.  And  it  is  necessary  that  these  Protozoa 
exist  in  such  great  numbers,  for  they  and  the  marine  one- 
celled  plants  (Protophyta)  supply  directly  or  indirectly 
the  food  for  all  the  other  animals  of  the  ocean. 
/Among  all  these  ocean  Protozoa  none  are  more  in- 
teresting than  those  belonging  to  the  two  orders  Forami- 
nifera  (fig.  1 1)  and  Radiolaria.  The  many  kinds  belong- 
ing to  these  orders  secrete  a  tiny  shell  (of  lime  in 
the  Foraminifera,  of  silica  in  the  Radiolaria)  which  en- 
closes most  of  the  one-celled  body.  These  minute  shells 
present  a  great  variety  of  shape  and  pattern,  many  being 
of  the  most  exquisite  symmetry  and  beauty.  The  shells 
are  perforated  by  many  small  holes  through  which  project 
long,  delicate,  protoplasmic  pseudopodia.  These  fine 
pseudopodia  often  interlace  and  fuse  when  they  touch  each 


BRANCH  PROTOZOA:    THE  ONE-CELLED  ANIMALS       81 

other,  thus  forming  a  sort  of  protoplasmic  network  outside 
of  the  shell.  In  some  cases  there  is  a  complete  layer  of 
protoplasm  — part  of  the  body  protoplasm  of  the  Protozoan 
— surrounding  the  cell  externally. 

When  these  tiny  animals  die  their  hard  shells  sink  to 
the  bottom  of  the  ocean,  and  accumulate  slowly,  in  in- 
conceivable numbers,  until  they  form  a  thick  bed  on  the 
ocean  floor.  Large  areas  of  the  bottom  of  the  Atlantic 


FIG.  II. — Rosalina  varians,  a  marine  protozoan  (Foraminifera)  with  calca- 
reous shell.     (After  Schultze.) 

Ocean  are  covered  with  this  slimy  ooze,  called  Forami- 
nifera ooze  or  Radiolaria  ooze,  depending  on  the  kinds  of 
animals  which  have  formed  it.  Nor  is  it  only  in  present 
times  that  there  has  been  a  forming  of  such  beds  by  the 
marine  Protozoa.  All  over  the  world  there  are  thick 
rock  strata  composed  almost  exclusively  of  the  fossil  shells 
of  these  simplest  animals.  The  chalk-beds  and  cliffs  of 
England,  and  of  France,  Greece,  Spain,  and  America, 
were  made  by  Foraminifera.  Where  now  is  land  were 
once  oceans  the  bottoms  of  which  have  been  gradually 


82  ELEMENTARY  ZOOLOGY 

lifted  above  the  water's  surface.  Similarly  the  rock 
called  Tripoli  found  in  Sicily  and  the  Barbadoes  earth 
from  the  island  of  Barbadoes  are  composed  of  the  shells 
of  ancient  Radiolaria. 

It  is  thus  evident  that  the  Protozoa  is  an  ancient  group 
of  animals.  As  a  matter  of  fact  zoologists  are  certain 
that  it  is  the  most  ancient  of  all  animal  groups.  All  of 
the  animals  of  the  ocean  depend  upon  the  marine  Protozoa 
and  the  marine  Protophyta,  one-celled  plants,  for  food. 
Either  they  feed  on  them  directly,  or  prey  on  animals 
which  in  turn  prey  on  these  simplest  organisms.  A  well- 
known  zoologist  has  said:  "The  food-supply  of  marine 
animals  consists  of  a  few  species  of  microscopic  organisms 
which  are  inexhaustible  and  the  only  source  of  food  for  all 
the  inhabitants  of  the  ocean.  The  supply  is  primeval  as 
well  as  inexhaustible,  and  all  the  life  of  the  ocean  has 
gradually  taken  shape  in  direct  dependence  on  it."  The 
marine  Protozoa  are  the  only  animals  which  live  in- 
dependently; they  alone  can  live  or  could  have  lived  in 
earlier  ages  without  depending  on  other  animals.  They 
must  therefore  be  the  oldest  of  marine  animals.  By 
oldest  is  meant  that  their  kind  appeared  earliest  in  the 
history  of  the  world,  and  as  it  is  certain  that  ocean  life  is 
older  than  terrestrial  life — that  is,  that  the  first  animals 
lived  in  the  ocean — it  is  obvious  that  the  marine  Protozoa 
are  the  most  ancient  of  all  animal  groups. 

As  already  learned  in  the  examination  of  examples  of 
one-celled  animals,  it  is  evident  that  life  may  be  success- 
fully maintained  without  a  complex  body  composed  of 
many  organs  performing  their  functions  in  a  specialized 
way.  The  marine  Protozoa  illustrate  this  fact  admirably. 
Despite  their  lack  of  special  organs  and  their  primi- 
tive way  of  performing  the  life-processes,  that  they  live 
successfully  is  shown  by  their  existence  in  such  extraor- 
dinary numbers.  They  outnumber  all  other  animals. 


BRANCE  PROTOZOA:    THE  ONE-CFLLED  ANIMALS       83 

The  conditions  of  life  in  the  surface-waters  of  the  ocean 
are  easy  and  constant,  and  a  simple  structure  and  simple 
method  of  performing  the  necessary  life-processes  are 
wholly  adequate  for  successful  life  under  these  con- 
ditions. 


CHAPTER    XVI 
BRANCH    PORIFERA:    THE    SPONGES 

THE    FRESH-WATER    SPONGE  (Spongilla  sp.) 

TECHNICAL  NOTE. — Fresh-water  sponges  may  perhaps  not  be 
readily  found  in  the  neighborhood  of  the  school,  but  they  occur 
over  most  of  the  United  States,  and  careful  searching  will  usually 
result  in  the  finding  of  specimens.  They  are  compact,  solid-looking 
masses,  sometimes  lobed,  resting  on  and  attached  to  rocks,  logs, 
timbers,  etc.,  in  clear  water  in  creeks,  ponds,  or  bayous.  They 
are  creamy,  yellowish-brown  or  even  greenish  in  color  and  resemble 
some  cushion-like  plant  far  more  than  any  of  the  familiar  animal 
forms.  They  can  be  distinguished  from  plants,  however,  by  the 
fact  that  there  are  no  leaves  in  the  mass,  nor  long  thread-like  fibres 
such  as  compose  the  masses  of  pond  algae  (pond  scum).  When 
touched  with  the  fingers  a  gritty  feeling  is  noticeable,  due  to  the 
presence  of  many  small  stiff  spicules.  Sponges  should  be  removed 
entire  from  the  substance  they  are  attached  to,  and  may  be  taken 
alive  to  the  laboratory.  They  die  soon,  however,  and  should  be  put 
into  alcohol  before  decay  begins. 

Note  the  form  of  the  sponge  mass.  Is  it  lobed  or 
branched  ?  Examine  the  surface  for  openings.  These 
are  of  two  sizes';  the  larger  are  osteoles  or  cxhalant  open- 
ings, while  the  smaller  and  more  numerous  are  pores  or 
inJialant  openings.  The  sponge-flesh  is  called  sarcode. 
Examine  a  bit  of  sarcode  under  the  microscope ;  note  the 
spicules.  Have  these  spicules  a  regular  arrangement  ? 
Of  what  are  they  composed  ? 

Draw  the  entire  sponge,  showing  shape  and  openings ; 
draw  some  of  the  spicules. 

Embedded  in  the  body-substance,  especially  near  the 
base,  note  (if  present)  numerous  small,  yellowish,  sub- 

84 


BRANCH  PORIFERA:   THE  SPONGES  85 

spherical  or  disk-like  bodies,  the  gemmnles.  These  are 
reproductive  bodies.  Each  gemmule  is  a  sort  of  internal 
bud.  It  is  composed  of  an  interior  group  of  protoplasmic 
cells,  enclosed  by  a  crust  thickly  covered  with  spicules. 
In  winter  the  sponge  dies  down  and  the  gemmnles  are  set 
free  in  the  water.  In  spring  the  protoplasmic  contents 
issue  through  an  aperture  in  the  crust,  called  the  micro- 
pyte  or  foraminal  opening,  and  develop  and  grow  into  a 
new  sponge. 

For  a  good  account  of  the  fresh- water  sponge,  see 
Pott's  "  Fresh-water  Sponges.  " 

A   CALCAREOUS   OCEAN-SPONGE  (Grantia  sp.)  (fig,  7,  D,  E,  F.) 

TECHNICAL  NOTE. — For  inland  schools,  specimens  preserved  in 
alcohol  or  formalin  must  be  used.  They  may  be  obtained  from 
dealers  in  naturalists'  supplies  (see  p.  453).  Specimens  of  some 
species  of  this  genus  can  be  obtained  at  almost  any  point  on  the 
Atlantic  or  Pacific  coasts  of  this  country. 

Examine  the  external  structure  of  a  specimen.  Note 
the  elongate,  sub-cylindrical  form,  the  attached  base,  the 
free  end.  Note  the  large  exhalant  opening,  osteole  or 
osculum,  at  the  free  end;  the  numerous  small  inhalant 
openings  elsewhere  on  the  surface  (best  seen  in  dried 
specimens).  Note  the  spicules  covering  the  surface  of  the 
body,  and  the  longer  ones  surrounding  the  osculum.  Cut 
the  sponge  in  two  longitudinally  and  note  the  simple  cylin- 
drical body-cavity,  the  gastric  cavity  or  cloaca.  Note  the 
thickness  of  the  body- wall ;  note  the  tubes  running  through 
the  body-wall  from  cloaca  to  external  surface.  Through 
these  tubes  water  laden  with  food  enters  the  gastric  cavity, 
where  the  food  is  digested,  the  water  and  undigested 
particles  passing  out  through  the  osculum.  Crush  a  bit  of 
dried  sponge,  or  boil  a  bit  of  soft  sponge  in  caustic  potash 
and  mount  on  a  glass  slide.  Examine  under  a  micro- 
scope and  note  the  abundance  of  spicules  and  the  variety 
in  their  form.  Two  kinds  may  always  be  found,  and 


86  ELEMENTARY  ZOOLOGY 

sometimes  three.  These  spicules  are  composed  of  car- 
bonate of  lime  and  can  be  dissolved  by  pouring  on  to 
them  a  drop  of  hydrochloric  acid. 

Some  of  the  sponges  may  have  buds  growing  out  from 
them  near  the  base.  These  buds  are  young  sponges 
developed  asexually.  If  allowed  to  develop  fully  the 
buds  would  have  detached  themselves  from  the  parent 
and  each  would  have  become  a  new  sponge. 

Make  drawings  showing  the  form  of  a  whole  sponge ; 
the  appearance  of  the  inner  face  of  the  sponge  bisected 
longitudinally;  the  shape  of  the  spicules. 

A   COMMERCIAL   SPONGE 

TECHNICAL  NOTE. — For  the  study  of  the  skeleton  of  an  ocean- 
sponge  with  more  complex  body  buy  several  common  small  bath- 
sponges  without  large  holes  running  entirely  through  them.  The 
teacher  should  have  also  a  few  specimens  of  small  marine  sponges 
preserved  in  alcohol  or  formalin.  Such  specimens  should  be  part 
of  the  laboratory  equipment  (see  account  of  laboratory  equipment, 
p.  450),  and  can  be  readily  and  cheaply  obtained  from  dealers  in 
naturalists'  supplies. 

The  bath-sponge  or  slate-sponge  consists  simply  of  the 
hard  parts  or  skeleton  of  a  sponge  animal.  In  life  all  of 
the  skeleton  is  enclosed  or  covered  by  a  soft,  tough  mass 
composed  of  layers  of  cells.  Note  the  many  openings  on 
the  surface  of  the  sponge.  Crush  a  bit  of  the  skeleton 
and  examine  it  under  the  microscope.  Note  that  it  is 
composed  of  fine  fibres  of  a  tough,  horny  substance  called 
spongin,  instead  of  tiny  distinct  calcareous  spicules. 

OTHER   SPONGES 

The  sponges  are  fixed,  plant-like  aquatic  animals. 
The  members  of  a  single  family  live  in  fresh  water,  being 
found  in  lakes,  rivers,  and  canals  in  all  parts  of  the  world. 
All  the  other  sponges,  and  there  are  several  thousand 
species  known,  live  in  the  ocean.  They  are  to  be  found 
at  all  depths,  some  in  shallow  water  near  the  shore  and 


BRANCH  PORIFERA:   THE  SPONGES 


others  in  deeper  water,  even  to  the  deepest  depths  yet 
explored.  They  are  found  in  all  seas,  though  especially 
abundantly  in  the  Atlantic  Ocean  and  Mediterranean  Sea. 
Form  and  size. — The  shape  of  the  simplest  sponges  is 
that  of  a  tiny  vase  or  nearly  cylindrical  cup,  hollow  and 
attached  at  its  base.  At  the  free  end  there  is  a  large 
opening.  But  there  is  a  great  deal  of  variety  in  the  form 
and  size  of  different  sponges. 
There  is,  indeed,  much  varia- 
tion in  the  shape  and  general 
character  of  different  individuals 
of  the  same  species.  Unlike 
most  other  animals,  sponges  are 
fixed,  and  the  character  of  the 
surface  to  which  a  sponge  is 
attached  has  much  influence 
upon  its  shape.  If  this  surface 
is  rough  and  uneven  the  sponge 
may  follow  in  its  growth  the 
sinuosities  of  the  surface  and  so 
become  uneven  and  distorted 
in  shape.  At  best,  only  a  few 
kinds  of  sponges  have  any  very 
even  and  symmetrical  shape. 
Most  of  them  are  very  unsym- 
metrical  and  grow  more  like  a 
low  compact  bushy  plant  than 
like  the  animals  we  are  familiar 
with.  The  smallest  sponges 
are  only  I  mm.  (^  in.)  high, 
while  the  largest  may  be  over FlG-  I2-  —  The  skeleton  of  a 

...  "glass  "  sponge  (skeleton  com- 

a  meter  (39  in.)  in  height.      In     posed  of  siliceous  spicules) from 
color    living    sponges    may    be     J;lP:xn-    <  From  specimen,  j 
red,  purple,   orange,   gray,   and    sometimes  blue.      Most 
sponges  have  the  whole  body  of  one  color. 


88  ELEMENTARY  ZOOLOGY 

Skeleton. —  A  very  few  sponges  have  no  skeleton  at 
all.  The  others  have  a  skeleton  or  hard  parts  composed 
of  interwoven  fibres  of  the  tough,  horny  substance  called 
spongin,  or  of  hosts  of  fine  needles  or  spicules  of  silica  or 
of  carbonate  of  lime.  The  siliceous  skeletons  of  some 
of  the  so-called  glass-sponges  (fig.  12)  are  very  beautiful. 
The  lime  and  siliceous  sponge  spicules  exhibit  a  great 
variety  of  outline,  some  being  anchor-shaped,  some  cross- 
shaped,  and  some  resembling  tiny  spears  or  javelins. 

Structure  of  body. — The  skeleton  of  a  sponge  whether 
composed  of  interlacing  fibres  or  of  short  spicules  is 
always  invisible  from  the  outside  when  the  sponge  is  alive. 
It  is  embedded  in,  or  clothed  by,  the  soft,  fleshy  part  of 
the  body.  The  soft  part  of  the  sponge  is  composed 
simply  of  two  layers  of  cells,  one  constituting  the  external 
surface  of  the  body,  and  the  other  lining  the  interior 
cavities  and  canals  of  the  body.  Between  these  two  cell- 
layers  there  is  a  mass  of  soft  gelatinous  substance  all 
through  which  protoplasm  ramifies,  and  in  which  are  em- 
bedded numerous  scattered  cells.  There  are,  as  seen  in 
the  case  of  Spongilla  and  Grantia,  no  systems  of  organs 
such  as  characterize  the  higher  animals.  No  heart,  lungs, 
alimentary  canal,  nervous  system,  organs  of  locomotion, 
eyes,  ears,  or  other  organs  of  special  sense;  the  sponge 
has  none  of  these.  It  is  simply  an  aggregate  of  cells, 
arranged  in  two  layers,  and  supported  usually  by  a  skele- 
ton of  horny  fibres  or  calcareous  or  siliceous  spicules.  Its 
body  is  usually  shapeless,  unsymmetrical  and  without 
front  or  back,  right  or  left.  It  is  not  to  be  wondered  at 
that  sponges  were  for  a  long  time  believed  to  be  plants. 

Feeding  habits. — The  sponges  feed  on  minute  bits  of 
animal  or  plant  substance  and  on  the  microscopic  unicel- 
lular plants  or  animals  which  float  in  the  water  which 
bathes  their  bodies.  The  water  entering  the  sponge- 
body  through  the  various  openings  of  the  surface  is  moved 


BRANCH  PORIFERA:   THE  SPONGES  89 

along  by  the  waving  or  lashing  of  the  flagella  of  the  cells 
which  line  the  canals,  and  these  currents  of  water  bear 
with  them  the  tiny  organisms  which  are  taken  up  by  these 
same  cells  and  digested.  The  incoming  currents  of  water 
meet  in  the  central  cavity  or  cavities  of  tiie  body  and  pass 
out  through  the  large  opening  called  the  osculum  at  the 
free  end  of  the  vase-like  body,  or  if  the  body  is  branched, 
through  the  large  openings  at  the  tips  of  these  branches. 

The  same  currents  of  water  bring  also  oxygen  for  the 
sponge's  breathing  and  carry  away  the  carbonic  acid  gas 
given  out  by  the  body-cells. 

As  a  German  naturalist  has  said,  the  one  necessary 
condition  for  the  life  of  a  sponge  is  the  streaming  of  water 
through  its  body.  All  sponges  have  a  system  of  canals 
for  this  water-current  and  all  have  means,  in  the  waving 
flagella  or  cilia  with  which  these  canals  are  lined,  for  pro- 
ducing these  currents.  When  a  live  sponge  is  put  into  a 
vessel  of  water,  currents  are  immediately  set  up,  and  they 
always  flow  into  the  body  through  the  many  fine  openings 
and  out  of  the  body  through  the  osculum. 

Development  and  life- history. — Although  the  sponge 
in  its  adult  condition  is  permanently  attached  by  its  base 
to  the  sea-bottom  or  to  some  rock  or  shell,  when  it  is  first 
born  it  is  an  active  free-swimming  creature.  The  sponges 
reproduce  in  two  ways,  asexually  and  sexually.  The 
asexual  mode  of  reproduction  of  the  fresh-water  sponge 
by  gemmules  has  already  been  described.  The  ocean 
sponges  also  reproduce  asexually  either  by  forming 
interior  gemmules  or  external  buds.  In  this  latter 
method  a  bud  forms  on  the  outer  surface  of  the  body 
which  increases  in  size  and  finally  grows  into  a  new 
sponge  individual.  In  some  species  this  new  sponge  does 
not  become  separated  from  the  body  of  the  mother, 
but  remains  attached  to  it  like  a  branch  to  a  tree-trunk. 
By  the  continued  production  of  such  non -separating  indi- 


90  ELEMENTARY  ZOOLOGY 

viduals,  a  colony  of  sponges  is  formed  which  has  the 
general  appearance  of  a  branching  plant.  In  other 
species  the  new  sponge  formed  by  the  development  and 
growth  of  a  bud  falls  off  and  becomes  a  distinct  separate 
individual. 

In  the  sexual  mode  of  reproduction,  male  or  sperm- 
cells  and  female  or  egg-cells  are  developed  in  the  same 
individual.  The  sperm-cells  are  motile  and  swim  about 
in  the  cavities  and  canals  of  the  sponge-body  until  they 
find  egg-cells,  which  they  fertilize.  The  fertilized  eggs 
begin  to  develop  and  pass  through  their  first  stages  in  the 
sponge-body.  Finally  the  embryo  sponge,  which  is 
usually  a  tiny  oval  or  egg-shaped  mass  of  cells,  escapes 
from  the  body  of  the  parent  into  the  water.  The  young 
sponge  has  some  of  its  outer  cells  provided  with  cilia, 
and  by  means  of  these  it  swims  about.  After  a  while 
it  comes  to  rest  on  the  ocean-floor  or  on  some  rock 
or  shell,  attaches  itself,  and  begins  to  take  on  the  form 
and  character  of  the  parent.  It  leads  hereafter  a  fixed 
sedentary  life. 

The  sponges  of  commerce. — The  sponge-skeletons 
which  are  the  ' '  sponges  ' '  that  we  use  all  belong  to  a  few 
species,  not  more  than  half  a  dozen.  Most  of  the  com- 
mercial sponges  come  from  the  Mediterranean  Sea,  though 
some  come  from  the  Bahama  Islands,  some  from  the  Red 
Sea,  and  a  few  from  the  coasts  of  Greece,  Asia  Minor, 
and  Africa.  The  commercial  sponges  do  not  live  in  very 
deep  water;  they  are  usually  found  not  deeper  than  200 
feet.  The  living  sponges  are  collected  by  divers,  or  are 
dragged  up  by  men  in  boats  using  long-poled  hooks,  or 
dredges.  « '  When  secured  they  are  exposed  to  the  air 
for  a  limited  time,  either  in  the  boats  or  on  shore,  and 
then  thrown  in  heaps  into  the  water  again  in  pens  or 
tanks  built  for  the  purpose.  Decay  thus  takes  place  with 
great  rapidity,  and  when  fully  decayed  they  are  fished  up 


BRANCH  PORIFERA:    THE  SPONGES  91 

again,  and  the  animal  matter  beaten,  squeezed,  or  washed 
out,  leaving  the  cleaned  skeleton  ready  for  the  market. 
In  this  condition  after  being  dried  and  sorted,  they  are 
sold  to  the  dealers,  who  have  them  trimmed,  re-sorted 
and  put  up  in  bales  or  on  strings  ready  for  exportation. 
There  are  many  modifications  of  these  processes  in  differ- 
ent places,  but  in  a  general  way  these  are  the  essentia- 
steps  through  which  the  sponge  passes  before  it  is  con- 
sidered suitable  for  domestic  purposes.  Bleaching- 
powders  or  acids  are  sometimes  used  to  lighten  the  color, 
but  these  unless  very  delicately  handled  injure  the  dura- 
bility of  the  fibres." 

Classification. — The  sponges  are  classified  according 
to  the  character  of  the  skeleton.  In  one  group  are  put 
all  those  sponges  which  have  a  skeleton  of  calcareous 
spicules,  and  this  group  is  called  the  Calcarea.  All  other 
sponges  are  grouped  as  Non-Calcarea,  the  members  of 
this  group  either  having  no  skeleton  at  all,  or  having  a 
skeleton  composed  of  siliceous  spicules  or  of  spongin 
fibres.  According  to  the  absence  or  presence  of  a  skele- 
ton and  the  character  of  the  skeleton  when  it  exists  the 
Non-Calcarea  are  subdivided  into  smaller  groups. 


CHAPTER    XVII 

BRANCH  OELENTERATA:  THE  POLYPS,  SEA- 
ANEMONES,   CORALS,    AND- JELLYFISHES 

The  structure  and  life-history  of  an  example  of  the 
polyps  (the  Fresh-water  Hydra,  Hydra  sp.)  has  been 
studied  in  Chapters  X  and  XI. 

OTHER     POLYPS,     SEA- ANEMONES,     CORALS,     AND 
JELLYFISHES 

TECHNICAL  NOTE. — The  teacher  should  have,  if  possible,  several 
pieces  of  coral  and  a  few  specimens  of  Coelenterates  in  alcohol  or 
formalin,  which  will  show  the  external  character,  at  least,  of  these 
animals  (see  account  of  laboratory  equipment,  p.  450).  If  the 
school  is  on  the  coast,  the  pupils  should  be  shown  the  sea-anemones 
of  the  tide-pools. 

The  animals  which  are  included  in  the  branch  Ccelen- 
terata  are,  at  least  in  living  condition,  unfamiliar  to  most 
of  us.  Like  the  sponges,  they  are  almost  all  inhabitants, 
of  the  ocean;  a  few,  like  Hydra,  live  in  fresh  water. 
Like  the  sponges,  too,  most  of  the  members  of  this 
branch  are  fixed,  and  in  their  general  appearance  suggest 
a  plant  rather  than  an  animal.  The  name  zoophytes,  or 
plant-animals,  which  is  often  applied  to  these  animals  is 
based  on  this  superficial  resemblance.  But  many  of  the 
Coelenterates  lead  an  active  free-swimming  life.  This  is 
true  of  the  jellyfishes  which  float  or  swim  about  on  or  near 
the  surface  of  the  ocea^P  Many  of  the  zoophytes  spend 
part  of  their  life  in  an  active  free-swimming  condition 

before  settling  down,   becoming  attached  and  thereafter 

92 


BRANCH  CCELENTERATA:   THE  POLYPS,  ETC.  93 

remaining  fixed.  In  localities  near  the  seashore  many 
animals  belonging  to  this  great  group  can  be  readily 
found  and  observed.  The  beautiful  sea-anemones  with 
their  slowly-waving  tentacles,  the  fine  many-branched 
truly  plant-like  hydroids  with  their  hosts  of  little  buds, 
and  the  soft  colorless  masses  of  jelly,  the  jellyfishes,  which 
are  cast  up  on  to  the  beaches  by  the  waves  are  all  animals 
belonging  to  the  branch  Coelenterata. 

General  form  and  organization  of  body. — The  general 
or  typical  plan  of  body-structure  for  the  Coelenterata, 
these  animals  which  come  next  to  the  sponges  in  degree 
of  complexity,  can  best  be  understood  by  imagining  the 
typical  cylindrical  or  vase-like  body  of  the  simple  sponges 
to  be  modified  in  the  following  way:  The  middle  one  of 
the  three  layers  of  the  body- wall  not  to  be  composed  of 
scattered  cells  in  a  gelatinous  matrix,  but  to  be  simply  a 
thin  non-cellular  membrane;  the  body-wall  not  to  be 
pierced  by  fine  openings  or  pores,  but  connected  with  the 
outside  only  by  the  single  large  opening  at  the  free  end, 
and  this  opening  to  be  surrounded  by  a  circlet  of  arm-like 
processes  or  tentacles,  which  are  continuations  of  the 
body-wall  and  similarly  composed.  Such  a  body-struc- 
ture, which  we  saw  well  shown  by  Hydra,  is  the  funda- 
mental one  for  all  polyps,  sea-anemones,  corals,  and 
jellyfishes.  The  variety  in  shape  of  the  body  and  the 
superficial  modifications  of  this  type-plan  are  many  and 
striking,  but  after  all  the  type-plan  is  recognizable  through- 
out the  whole  of  this  great  group  of  animals. 
C  The  two  chief  body-shapes  represented  in  the  branch 
are  those  of  the  polyps  on  the  one  hand,  and  the  jelly- 
fishes  or  medusae  oTT  the  other.  The  polyp-shape  is  that 
of  a  tube  with  a  basal  end  blirrS^or  closed,  attached  to 
some  firm  object  in  the  water  ana  with  the  free  end  with 
an  opening,  the  mouth-opening.  At  this  mouth-end 
there  is  a  circlet  of  movable,  very  contractile  tentacles. 


94  ELEMENTARY  ZOOLOGY 

The  mouth  may  open  directly  into  the  interior  of  the 
which  interior  may  be  called  the  digestive  cavity 
may  lead  into  a  simple  short  tube  produced  by  t 
vagination  or  bending  in  of  the  body-wall,  which  m 
looked    on    as    the    simplest  kind   of    oesophagus, 
oesophageal  tube  opens  into  the  body-cavity  or  dige^u\/e 
cavity.      This    cavity    may    be  incompletely   divided    by 
longitudinal  partitions  which  project  from  the  sides  in'.o 
the  cavity. 

The  jellyfish  or  medusoid  body-form  corresponds^  *,. 
general  to  an  umbrella  or  bell.  Around  the  edge  of  this 
umbrella  are  disposed  numerous  threads  or  tentacles 
(corresponding  to  the  circlet  of  tentacles  in  the  polyp). 
The  mouth-opening  is  at  the  end  of  a  longer  or  shorter 
projection  which  hangs  down  from  the  middle  of  the 
under  side  of  the  umbrella.  The  interior  body-cavity  or 
digestive  cavity  extends  out  into  the  umbrella-shaped 
part  of  the  body,  usually  in  the  condition  of  canals  radiat- 
ing from  the  centre  and  a  connecting  canal  running 
around  the  margin  of  the  umbrella. 

Structure. — Although  the  Ccelenterata  show  little  in- 
dication of  the  complex  composition  of  the  body  out  of 
organs,  as  it  exists^  among  the  higher  animals,  yet  they 
do  show  an  nr|rnfcfokribLe-  advance  on  the  simple,  almost 
organless  body  of  the  sponges.  This  is  chiefly  shown  by 
the  differentiation  among  the  cells  which  compose  the 
body.  In  the  polyps  and  jellyfishes  some  of  the  cells  are 
specialized  to  be  nnrnjgfal'aKlp  muscle-cells,  some  to  be 
\  nerve-cells  and  fibres,  and  so  on.  A  very  simple  nervous 
system  consisting  of  small  groups  of  nerve-cells  connected 
by  nerve-fibres  exists.  Some  very  simple  special  sense- 
organs  may  occur.  The  digestive  system,  although  in 
the  simpler  Coelenterates  consisting  merely  of  the  cylin- 
drical body-cavity  enclosed  by  the  body- wall  and  opening 
by  the  single  hole  at  the  free  end  of  the  body,  in  some  is 


BRANCH  CCELENTERATA :    THE  POLYPS,  ETC.  95 

complex  and  is  composed  of  different  parts.  Those 
iterates  which  are  not  fixed  but  lead  an  active,  free- 
zing life,  viz.,  the  jellyfishes  or  medusae,  are  the 
highly  organized. 

ie  tentacles  which  surround  the  mouth-opening  and 

U*    j  to  grasp  food  and  carry  it  into  the  mouth,  and  the 

stinging  or  lasso  threads  with  which  these  tentacles  are 

provided  are  special  organs  possessed  by  most  of  these 

jials. 

^  Skeleton. — Like  the  sponges,  some  of  the  Ccelenterata 
possess  a  hard  skeleton.  This  skeleton  is  always  com- 
posed of  calcium  carbonate  and  is  called  coral.  Those 
polyps  which  form  such  a  skeleton  are  called  the  corals. 
Coral  will  be  described  in  connection  with  the  account  of 
the  coral-polyps. 

_yc  Development  and  life-history. — The  polyps  and  jelly- 
fishes  reproduce  both  asexually  and  sexually.  The 
asexual  mode  is  usually  that  of  budding.  On  a  polyp  a 
bud  is  formed  by  a  hollow  outgrowth  of  the  body-wall. 
The  bud  grows,  an  opening  appears  at  its  distal  end,  a 
circlet  of  tentacles  arises  about  this  mouth-opening  and  a 
new  polyp  individual  is  formed.  This  individual  may 
separate  from  the  parent  or  it  may  remain  attached  to  it. 
By  the  development  of  numerous  buds,  and  the  remaining 
attached  of  all  of  the  individuals  developing  from  these 
buds,  a  colony  of  polyp  individuals  may  be  formed,  plant- 
like  in  appearance.  The  various  polyp  individuals  of  a 
colony  may  differ  somewhat  among  themselves,  and  these 
differences  are  correlated  with  a  division  of  labor.  Thus 
some  of  the  individuals  may  devote  themselves  to  getting 
food  for  the  colony,  and  these  have  mouth  and  tentacles. 
Others  may  be  devoted  to  the  production  of  new  indi- 
viduals by  budding  or  by  producing  germ-cells,  and  may 
not  have  any  mouth-opening  or  any  food-grasping 
tentacles. 


96  ELEMENTARY  ZOOLOGY 

In  case  of  many  polyps  all  or  some  of  the  new  indi- 
viduals which  arise  by  budding  do  not  become  polyps,  but 
develop  into  medusae  or  jellyfish,  which  separate  from  the 
fixed  polyp  and  swim  off  through  the  water.  These 
medusae  or  jellyfish  produce  sperm-cells  and  egg-cells. 
The  sperm-cells  fertilize  the  egg-cells  and  a  new  indi- 
vidual develops  from  each  fertilized  egg.  This  new  indi- 
vidual is  at  first  an  active  free-swimming  larva  called  a 
planula,  which  does  not  resemble  either  a  medusa  or  polyp. 
After  a  while  it  settles  down,  becomes  fixed  and  develops 
into  a  polyp.  Thus  a  polyp  may  produce  a  medusa  or 
jellyfish  which,  however,  produces  not  a  new  jellyfish,  but 
a  polyp.  This  is  called  an  alter  nation  _gf  generations . 
and  is  not  an  uncommon  phenomenon  among  the  lower 
animals,  j  It  results  from  such  an  alternation  of  genera- 
tions that  a  single  species  of  animal  may  have  two  distinct 
forms.  This  having  two  different  forms  is  called  diino}'- 
pJiism.  Sometimes,  indeed,  a  species  may  appear  in 
more  than  two  different  forms ;  such  a  condition  is  called 
polymorphj^tn . 

Not  all  medusae  or  jellyfish  are  produced  by  polyp  indi- 
viduals, nor  do  jellyfish  always  produce  polyps  and  not 
jellyfishes.      There    are  some   jellyfishes  (we  might   call 
them  the  true  jellyfishes)  which  always  have  the  jellyfish 
form,  producing  new  jellyfishes  either  by  budding  or  by 
eggs,  and  there  are  some  polyps  which  always  have  the 
true  polyp  form,    producing    new  individuals,    either    by 
budding  or  by  eggs,  always  of  polyp  form  and  never  of 
jellyfish    form.      That    is,   some    species    of   Ccelenterata 
exist  only  in  polyp  form,  some  species  exist  only  in  jelly- 
fish form,  while  some  species  (those  having  an  alternation 
of  generations)  exist  in    both  polyp  and  jellyfish  form,  ] 
these  two  forms  appearing  as  alternate  generations. 
/         Classification. — The    branch    Ccelenterata    is    divided  f 
^  four  classes:   (i)  the  Hydrozoa,  including  the  fresh- 


BRANCH  CCELENTER/1T/I :    THE  POLYPS,  ETC. 


97 


water  polyps,  numer- 
ous marine  polyps, 
many  small  jellyfishes 
and  a  few  corals ;  (2) 
the  Scyphozoa,  includ- 
ing most  of  the  large 
jellyfishes;  (3)  the  Ac - 
tinozoa,  including  the 
sea-anemones  and 
most  "of  the  stony 
corals;  (4)  the  Cte- 
nophora,  including 
certain  peculiar  jelly- 
fishes. - 

The  polyps,  colonial 
jellyfishes,  etc.  (Hy- 
drozoa). — To  the  class 
Hydrozoa  belongs  the 
Hydra  already  studied . 
There  are  a  few  other 
fresh-water  polyps  and 
they  all  belong  to  this 
class.  The  most  in- 
teresting members  of 
the  class  are  the  "co- 
lonial jellyfishes," 
constituting  the  order 
Siphonophora.  These 

FIG.    13.  -The    Portuguese  M;m-of-War  (Physalia  sp.).      (From  specimen 


98  ELEMENTARY  ZOOLOGY 

colonial  je-llyfishes  are  floating  or  swimming  colonies  of 
polypoid  and  medusoid  individuals  in  which  there  is  a 
marked  division  of  labor  among  the  individuals,  ac- 
companied by  marked  differences  in  structural  charac- 
ter. The  individuals  are  accordingly  polymorphic, 
that  is,  appear  in  various  forms,  although  all  belong 
to  the  same  species.  Because  these  various  individuals 
forming  a  colony  have  given  up  very  largely  their 
individuality,  combining  together  and  acting  together  like 
the  organs  of  a  complex  animal,  they  are  usually  not 
called  individuals,  nor  on  the  other  hand  organs,  but 
zooids,  or  animal-like  structures.  The  beautiful  "  Portu- 
guese man-of-war  "  (fig.  13)  is  one  of  these  colonial  jelly- 
fishes.  It  appears  as  a  delicate  bladder-like  float,  brilliant 
blue  or  orange  in  color,  usually  about  six  inches  long, 
and  bearing  on  its  upper  surface  which  projects  above  the 
water  a  raised  parti-colored  crest,  and  on  its  under  surface 
a  tangle  of  various  appendages,  thread-like  with  grape- 
like  clusters  of  little  bell-  or  pear-shaped  bodies.  Each 
of  these  parts  is  a  peculiarly  modified  polyp-  or  medusa- 
zooid  produced  by  budding  from  an  original  central  zooid. 
The  Portuguese  man-of-war  is  very  common  in  tropical 
oceans,  and  sometimes  vast  numbers  swimming  together 
make  the  surface  of  the  ocean  look  like  a  splendid  flower- 
garden. 

Usually  the  central  zooid  in  a  Siphonophore  to  which 
the  other  zooids  are  attached  is  not  a  bladder-like  float, 
but  is  an  upright  tube  of  greater  or  less  length.  In  the 
Siphonophore  shown  in  figure  14,  the  compound  body  is 
composed  of  a  long  central  hollow  stem  with  hundreds 
or  thousands  of  variously  shaped  parts,  each  of  which  is 
reducible  to  either  a  polyp  or  medusazooid,  attached 
around  it.  The  upper  end  is  enlarged  to  form  an  air- 
filled  chamber,  a  sac-like  boat,  by  means  of  which  the 
whole  colony  is  kept  afloat.  Around  the  uprjer  end  of  the 


BRANCH  CCELEKTERATA:    THE  POLYPS,  ETC. 


99 


central  stem  are  many  medusoid  structures,  the  swimming- 
bells,  by  means  of 
whose  opening  and 
closing  the  whole  col- 
ony is  made  to  swim 
through  the  water. 
Each  swimming  -  bell 
is  a  modified  medusa- 
zooid,  without  tenta- 
cles, without  digestive 
or  reproductive  or- 
gans, but  exercising 
the  power  of  swim- 
ming by  contracting 
and  forcing  the  water 
out  of  the  hollow  bell 
just  as  is  done  by 
the  free  medusae.  Be- 
low the  swimming- 
bells,  at  the  lower  end 
of  the  central  stem, 
are  grouped  many 
structures  presenting 
at  first  sight  a  confu- 
sion of  variety  and 
complexity,  but  on 
careful  examination 
revealing  themselves 
to  be  polyp-  and  me- 
dusa-zooids  modified 
to  form  at  least  five 

kinds    of  particularly   . 

FTG.  14. — A  colonial  jelly  fish  (Siphonophora). 

functioning  Struc-  (After  Haeckel.) 

tures.     There  are  many  flattened  scale-like  parts  whose 
function  is  simply  that  of  affording  a  passive  protection, 


ioo  ELEMENTARY  ZOOLOGY 

in  times  of  danger,  to  the  other  structures.  These  pro- 
tecting-scales  are  greatly  modified  medusa-zooids,  each 
consisting  of  a  simple  cartilage-like  gelatinous  mass 
penetrated  by  a  food-carrying  canal.  Under  the  broad 
leaves  of  these  protecting-zooids  are  a  number  of  pear- 
shaped  bodies  which  have  a  wide  octagonal  mouth-open- 
ing at  their  free  end,  and  possess  in  their  interior  certain 
digestive  glands.  Each  one  is  provided  with  a  very  long 
flexible  tentacle  which  bears  many  fine  stinging-threads. 
The  tentacle  waves  back  and  forth  in  the  water,  and 
on  coming  in  contact  with  an  enemy  or  with  prey  its 
poisonous  stinging-threads  shoot  out  and  paralyze  or 
wound  the  unfortunate  animal.  These  pear-shaped  bodies 
are  the  feeding  structures,  each  being  a  modified  polyp- 
zooid.  Scattered  among  these  dangerous  structures  are 
many  somewhat  similarly  shaped  but  wholly  harmless 
structures,  the  sense-structures.  Each  of  these  has  a 
pear-shaped  body  but  without  mouth-opening,  and  also 
a  long,  very  sensitive,  tentacle-like  process.  The  sense 
of  feeling  is  highly  developed  in  these  tentacles,  and  they 
discover  for  the  colony  the  presence  of  any  strange  body. 
These  sense-structures  are  modified  polyp-zooids.  Finally 
there  are  two  other  kinds  of  structures,  usually  arranged 
in  groups  like  bunches  of  grapes,  which  are  the  repro- 
ductive structures,  male  and  female.  They  are  modified 
medusa-zooids  grown  together  and  without  tentacles. 
This  whole  colony,  or  this  compound  animal,  floats  or 
swims  about  at  the  surface  of  the  ocean,  and  performs  all 
of  the  necessary  functions  of  life  as  a  single  animal  com- 
posed of  organs  might.  Yet  the  Siphonophore  is  more 
truly  to  be  regarded  as  a  community  in  which  the  hundreds 
or  thousands  of  animals,  representing  five  or  six  kinds  of 
individuals,  all  of  one  species,  are  fastened  together.  Each 
individual  performs  the  particular  duties  devolving  upon 
its  kind  or  class.  Thus  there  are  food-gathering  indi- 


BRANCH  CCELENTERATA :   THE  POLYPS,  ETC.        ior 

viduals,  locomotor  individuals,  sense  individuals,  and 
reproductive  individuals.  The  modifications  of  the  various 
kinds  of  individuals  are  more  extreme  than  in  the  case  of 
the  various  kinds  of  individuals  composing  a  bee-com- 
munity, for  example,  but  the  holding  together  or  fusing 
of  all  into  one  body  or  corporation  is  a  condition  which 
makes  this  greater  modification  necessary  and  not  un- 
expected. And  there  is  no  difficulty  in  seeing  that  each 
of  these  parts  is  really,  structurally  considered,  a  modified 
polyp  or  medusa. 

The  large  jellyfishes,  etc.  (Scyphozoa). — To  the  class 
Scyphozoa  belong  most  of  the  common  large  jellyfishes. 


FIG.    15. — A  jellyfish    or   medusa,    Gonionema   vertens,  eating   two   small 
fishes.     (From  specimen  from  Atlantic  Coast.) 

When  one  walks  along  the  sea-beach  soon  after  a  storm 
one  may  find  many  shapeless  masses  of  a  clear  jelly-like 


102  ELEMENTARY  ZOOLOGY 

substance  scattered  here  and  there  on  the  sand.  These 
are  the  bodies  or  parts  of  bodies  of  jellyfishes  which  have 
been  cast  up  by  the  waves.  Exposed  to  the  sun  and 
wind  the  jelly-like  mass  soon  dries  or  evaporates  away  to 
a  small  shrivelled  mass.  The  body-substance  of  a  jelly- 
fish contains  a  very  large  proportion  of  water;  in  fact 
there  is  hardly  more  than  I  per  cent  of  solid  matter  in  it. 

The  jellyfishes  occur  in  great  numbers  6n  the  surface  of 
the  ocean  and  are  familiar  to  sailors  under  the  name  of 
"sea-bulbs."  Some  live  in  the  deeper  waters;  a  few 
specimens  have  been  dredged  up  from  depths  of  a  mile 
below  the  surface.  They  range  in  size  from  "  umbrellas  " 
or  disks  a  few  millimeters  in  diameter  to  disks  of  a 
diameter  of  two  meters  (2\  yards).  'They  are  all  car- 
nivorous, preying  on  other  small  ocean  animals  which 
they  catch  by  means  of  their  tentacles  provided  with 
stinging-threads.  The  tentacles  of  some  of  the  largest 
jellyfishes  "reach  the  astonishing  length  of  40  meters,  or 
about  130  feet."  Many  of  the  jellyfishes  are  beautifully 
colored,  although  all  are  nearly  transparent.  Almost  all 
of  them  are  phosphorescent,  and  when  irritated  some 
emit  a  very  strong  light. 

The  sea-anemones  and  corals  (Actinozoa). — Almost 
everywhere  along  the  seashore  where  there  are  rocks  and 
tide-pools  a  host  of  various  kinds  of  sea-anemones  can  be 
found.  When  the  tide  is  out,  exposing  the  dripping  sea- 
weed-covered rocks,  and  the  little  sand-  or  stone-floored 
basins  are  left  filled  with  clear  sea-water,  the  brown  and 
green  and  purple  "sea-flowers  "  may  be  found  fixed  to 
the  rocks  by  the  base  with  the  mouth-opening  and  circlet 
of  slowly-moving  tentacles  hungrily  ready  for  food 
(fig.  1 6).  Touch  the  fringe  of  tentacles  with  your  finger- 
tip and  feel  how  they  cling  to  it  and  see  how  they  close  in 
so  as  to  carry  what  they  feel  into  the  mouth-opening.  A 
host  of  individuals  there  are,  and  scores  of  different  kinds; 


BRANCH  CCELEHTERATA :    THE  POLYPS,  ETC.          103 

some  small,  some  large,  some  with  the  body  covered  out- 
side with  tiny  bits  of  stone  and  shell  so  that  they  are 
hardly  to  be  distinguished  from  the  rock  to  which  they 


FIG.  16. — Sea  anemones,  Bunodes  californica,  open  and  .closed  individuals. 
The  closed-  individuals  in  upper  right-hand  corner  show  the  external 
covering  of  small  bits  of  rock  and  shell,  characteristic  of  most  individu- 
als of  this  species.  (From  living  specimens  in  a  tide-pool  on  the  Bay 
of  Monterey,  California.) 

cling;  some  of  bright  and  showy  colors.      These  are  the 
most  familiar  members  of  the  class  Actinozoa. 

But  in  other  oceans,  along  the  coasts  of  other  lands, 
especially  those  of  the  tropics  and  sub-tropics,  there  are 


104  ELEMENTARY  ZOOLOGY 

some  other  members  of  the  class  which  are  of  unusual 
interest.  They  are  the  corals,  or  coral  polyps.  We 
know  these  animals  chiefly  by  their  skeletons  (fig.  17). 
The  specimens  of  corals  which  one  sees  in  collections,  or 
made  into  ornaments,  are  the  calcareous  skeletons  of 
various  kinds  of  the  coral  polyps.  Some  of  the  corals 
live  together  in  enormous  numbers,  forming  branching 
colonies  fixed  as  closely  together  as  possible,  and  secrete 
while  living  a  stony  skeleton  of  carbonate  of  lime.  These 
skeletons  persist  after  the  death  of  the  animals,  and 
\)f  cause  of  their  abundance  and  close  massing  form  great 
reefs  or  banks  and  islands.  These  coral  reefs  and  islands 
occur  only  in  the  warmer  oceans.  In  the  Atlantic  they 
are  found  along  the  coasts  of  Southern  Florida,  Brazil 
and  the  West  Indies ;  in  the  Pacific  and  Indian  Oceans 
there  are  great  coral  reefs  on  the  coast  of  Australia^ 
Madagascar  and  elsewhere,  and  certain  large  groups  of  in- 
habited islands  like  the  Fiji,  Society,  and  Friendly  Islands 
are  exclusively  of  coral  formation.  Coral  islands  have  a 
great  variety  of  form,  although  the  elongated,  circular, 
ring-shaped  and  crescent  forms  predominate.  How  such 
islands  are  first  formed  is  described  as  follows  by  a  well- 
known  student  of  corals: 

"A  growing  coral  plantation,  with  its  multitudinous 
life,  oftentimes  arises  from  great  depths  of  the  ocean,  and 
the  sea-bed  upon  which  it  rests  is  probably  a  submarine 
bank  or  mountain,  upon  which  have  lodged  and  slowly 
aggregated  the  hard  skeletons  of  pelagic  forms  of  life. 
WThen,  through  various  sources  of  increase,  this  submarine 
bank  approaches  the  depth  of  from  one  hundred  to  one 
hundred  and  fifty  feet  from  the  surface  of  the  water,  there 
begins  on  its  top  a  most  wonderful  vital  activity.  It  is 
then  within  the  bathymetric  zone  of  the  reef-building 
corals.  Of  the  many  groups  of  marine  life  which  tnen 
'cake  possession  of  the  bank,  corals  are  not  the  only 


BRANCH  CCELEUTERATA  :    THE   POLYPS,   ETC.         105 

animals,  but  they  are  the  most  important,  as  far  as  its 
subsequent  history  goes.  As  the  bank  slowly  rises  by 
their  growth,  it  at  last  approaches  the  surface  of  the 
water,  and  at  low  tide  the  tips  of  the  growing  branches 
of  coral  are  exposed  to  the  air.  This,  however,  only 
takes  place  in  sheltered  localities,  for  long  before  it  has 
reached  this  elevation  it  has  begun  to  be  more  or  less 


FIG.    17. — Skeleton  of  a   branching  coral,  Madrepora  cervicornis.     (From 

specimen.) 

changed  and  broken  by  the  force  of  the  waves.  As  the 
submarine  bank  approaches  the  tide  level,  the  delicate 
branching  forms  have  to  meet  a  terrific  wave-action. 
Fragments  of  the  branching  corals  are  broken  off  from 
the  bank  by  force  of  the  waves,  and  falling  down  into  the 
midst  of  the  growing  coral  below  fill  up  the  interstices, 


io6  ELEMENTARY  ZOOLOGY 

and  thus  render  the  whole  mass  more  compact.  At  the 
same  time  larger  fragments  are  broken  and  rolled  about 
by  the  waves  and  are  eventually  washed  up  into  banks 
upon  the  coral  plantation,  so  that  the  island  now  appears 
slightly  elevated  above  the  tides.  This  may  be  called  a 
first  stage  in  the  development  of  a  coral  island.  It  is, 
however,  little  more  than  a  low  ridge  of  worn  fragments 
of  coral  washed  by  the  high  tides  and  swept  by  the  larger 
waves — a  low,  narrow  island  resting  on  a  large  submarine 
bank." 

When  the  coral  island  rises  thus  a  little  above  the  sur- 
face of  the  water,  the  waves  break  up  some  of  the  coral 
into  fine  sand,  which  fills  in  the  interstices,  and  offers  a 
sort  of  soil  in  which  may  germinate  seeds  brought  in  the 
dried  mud  on  the  feet  of  ocean  birds  or  carried  by  the 
ocean  currents.  With  the  beginning  of  vegetable  growth 
the  soil  is  more  firmly  held,  is  fertilized  and  ready  for  the 
seeds  of  plants  which  need  a  better  soil  than  lime  sand. 
Flying  insects  find  their  way  to  the  island,  especially  if 
it  be  near  the  mainland,  birds  begin  to  nest  on  it,  and 
soon  it  may  be  the  seat  of  a  luxuriant  plant  and  animal 
life. 

For  an  account  of  coral  islands  see  Darwin's  "The 
Structure  and  Distribution  of  Coral  Reefs." 
I  There  are  over  2000  kinds  of  coral  polyp  known,  and 
/  their  skeletons  vary  much  in  appearance.  Because  of  the 
appearance  of  the  skeleton  certain  corals  have  received 
common  names,  as  the  organ-pipe  coral,  brain  coral,  etc. 
The  red  coral,  of  which  jewelry  is  made,  grows  chiefly  in 
the  Mediterranean.  It  is  gathered  especially  on  the 
western  coast  of  Italy,  and  on  the  coasts  of  Sicily  and 
Sardinia.  Most  of  this  coral  is  sent  to  Naples,  where  it  is 
cut  into  ornaments. 

There    are    other    interesting    members    of    the    class 
f  Actinozoa  like  the  beautiful    sea-pens,   sea-feathers   and 


BRANCH  CCELENTERATA :    THE  POLYPS,  ETC.         107 

sea-fans,   delicate,   branching,   tree-like    forms    found  all 
over  the  world. 

J  Ctenophora. — The  members  of  this  class  are  mostly 
small,  peculiar  jellyfishes  which  do  not  form  colonies,  and 
are  extremely  delicate,  being  usually  perfectly  trans- 
parent. They  swim  by  means  of  cilia.  They  never 
appear  in  a  polyp  condition,  but  are  always  medusoid  in 
shape. 


CHAPTER    XVIII 

BRANCH      ECHINODERMATA  :       STARFISHES, 
SEA-URCHINS,   SEA-CUCUMBERS 

STARFISH  (Asterias  sp.) 

TECHNICAL  NOTE. — The  species  of  Asterias  are  widely  dis- 
tributed on  both  coasts  of  the  United  States  and  may  be  procured 
on  almost  any  rocky  shore  at  low  tide.  Teachers  in  inland  schools 
can  obtain  preserved  material  from  the  dealers  mentioned  on  p. 
453.  Most  of  the  specimens  should  be  placed  in  alcohol  or  4$ 
formalin.  If  fresh  material  can  be  had  it  is  well  to  place  at  least . 
one  specimen  for  each  student  in  a  20%  solution  of  nitric  acid  in 
water  for  two  or  three  hours,  when  all  of  the  calcareous  parts  will 
have  been  dissolved,  and  after  a  thorough  washing  the  specimen 
will  be  ready  for  use. 

External  structure  (figs.  18  and  19.) — In  a  fresh 
specimen  or  one  which  has  been  preserved  in  alcohol  or 
formalin  note  the  raying  out  of  parts  of  the  body  from  a 
common  centre.  This  is  characteristic  of  the  body  or- 
ganization of  all  Echinoderms,  and  is  known  as  radial 
symmetry.  The  lower  surface  of  the  body  is  called  the 
oral  (because  the  mouth  is  on  this  surface),  while  the 
upper  is  called  the  aboral  surface.  The  central  part  of 
the  body  is  called  the  disk.  Note  on  the  aboral  surface 
of  the  disk  a  small  striated  calcareous  plate,  the  madre- 
porite  or  madrcporic  plate.  In  the  middle  (or  very 
nearly  in  the  middle)  of  this  surface  of  the  disk  there  is 
a  small  pore,  the  anal  opening.  The  entire  aboral  sur- 
face as  well  as  a  greater  part  of  the  oral  side  is  thickly 
studded  with  the  calcareous  ossicles  of  the  body-wall. 
These  ossicles  support  numerous  short  stout  spines  ar- 
ranged in  irregular  rows.  Note  that  some  of  the  ossicles 

108 


BRANCH  ECH1NODERMATA :  STARFISHES,  ETC.        109 

support  certain  very  small  pincer-like  processes,  the  pedi- 
cellarice.  In  the  interspaces  between  the  calcareous  plates 
are  soft  fringe-like  projections  of  the  inner  body-lining,  the 


— -eye  spot 


''cardiac  stomach 

r^V^" "  -  intestinal  caecu. 


pyloric  caecuik 
'  muscles  of  tht  pyloric  caeca 


eye  spot--' 


FIG.  18. — Dissection  of  a  starfish  (Asterias  sp.). 

respiratory  cceca.  Note  at  the  tip  of  each  arm  or  ray  a 
cluster  of  small  calcareous  ossicles  and  within  each  cluster 
a  small  speck  of  red  pigment,  the  eye-spot  or  ocellus. 


no  ELEMENTARY  ZOOLOGY 

Make  a  drawing  of  the  aboral  surface  showing  all  these 
parts. 

On  the  oral  surface  note  the  centrally-located  mouth, 
the  ambulacral  groove 's,  one  running  longitudinally  along 
each  ray,  and  in  each  groove  two  double  rows  of  soft 
tubular  bodies  with  sucker-like  tips.  These  are  called 
the  tube-feet  and  are  organs  of  locomotion.  Make  a 
drawing  of  the  oral  surface. 

Internal  structure  (figs.  18  and  19).— TECHNICAL  NOTE.— 
Take  a  specimen  which  has  been  immersed  for  some  time  in  the  nitric 
acid  solution,  and  with  a  strong  pair  of  scissors,  or  better,  bone- 
cutters,  cut  away  all  the  aboral  wall  of  the  disk  except  that  immedi- 
ately around  the  madreporite  and  the  anus.  Now  begin  at  the  tip 
of  each  ray  and  cut  away  the  aboral  wall  of  each,  leaving,  however, 
a  single  arm  intact.  When  the  roof  of  each  arm  has  been  carefully 
dissected  away  the  specimen  should  appear  as  in  fig.  18. 

Note  the  large  alimentary  canal,  which  is  divided  into 
several  regions.  Note  the  short  cesophagus  leading  from 
the  mouth  on  the  oral  surface  directly  into  a  large  mem- 
branous pouch,  the  cardiac  portion  of  the  stomach.  By 
a  short  constriction  the  cardiac  portion  is  separated  from 
the  part  which  lies  just  above,  i.e.,  the  pyloric  portion  of 
the  stomach.  From  the  pyloric  portion  large,  pointed, 
paired  glandular  appendages  extend  into  each  ray. 
These  are  the  pyloric  cceca.  Their  function  is  digestive, 
and  oftentimes  they  are  spoken  of  as  the  digestive  glands 
or  "livers."  The  pyloric  caeca,  as  well  as  the  cardiac 
portion  of  the  stomach,  are  held  in  place  by  paired  muscles 
which  extend  into  each  arm.  Note  two  sets  of  these 
muscles,  one  set  for  thrusting  the  cardiac  portion  of  the 
stomach  out  through  the  mouth  and  another  for  pulling  it 
back,  the  protractor  muscles  and  retractor  muscks, 
respectively.  The  starfish  obtains  its  food  by  enclosing 
it  in  its  everted  stomach  and  then  withdrawing  stomach 
and  food  into  the  body.  Note  that  the  pyloric  portion  of 
the  stomach  opens  aoove  into  a  short  intestine  terminating 


BRANCH  ECHINODERMATA  :  STARFISHES,  ETC.         in 

in  the  anus,  and  observe  that  there  is  attached  to  the  in- 
testine a  convoluted  many-branched  tube,  the  intestinal 
ccecum. 

Carefully  remove  a  pair  of  pyloric  caeca  from  one  of  the 
rays  and  note  the  short  duct  which  connects  them  with 
the  pyloric  chamber  of  the  stomach.  Note  in  the  angle 
of  each  two  adjoining  rays  paired  glandular  masses  which 
empty  by  a  common  duct  on  the  aboral  surface.  These 
glands  are  the  reproductive  organs.  Note  the  small  bulb- 
like  bladders  extending  in  two  double  rows  on  the  floor 
of  each  ray.  These  are  the  water-sacs  or  ampulla,  and 
each  one  is  connected  directly  with  one  of  the  locomotor 
organs,  the  tube-feet. 

Make  a  drawing  of  the  organs  in  the  dissection  which 
have  so  far  been  studied. 

TECHNICAL  NOTE. — For  a  careful  study  of  the  locomotor  organs 
a  fresh  starfish  should  be  injected.  This  can  usually  be  accom- 
plished by  cutting  one  ray  off  squarely,  and  inserting  the  needle  of 
a  hypodermic  syringe  (which  has  been  previously  filled  with  a 
watery  solution  of  carmine  or  Berlin  blue),  into  the  end  of  the 
radial  water-tube  which  runs  along  the  floor  of  the  ray.  By 
injecting  here,  the  whole  system  of  vessels,  tube-feet,  and  ampullae 
are  filled. 

Note  a  ring-shaped  canal  which  passes  around  the 
alimentary  canal  near  the  mouth  from  which  radial  vessels 
run  out  beneath  the  floor  of  each  ray  and  from  which  a 
hard  tube  extends  to  the  madreporite.  This  hard  tube  is 
the  stone  canal,  so  called  because  its  walls  contain  a  series 
of  calcareous  rings,  while  the  circular  tube  is  the  ring 
canal  or  circum-oral  water-ring  from  which  radiate  the 
radial  canals.  In  some  species  of  starfish  there  are 
bladder-like  reservoirs,  Polian  vesicles,  which  extend 
interradially  from  the  ring  canal. 

Note  that  the  ampullae  and  tube-feet  are  all  connected 
with  the  radial  canals.  By  a  contraction  of  the  delicate 


112 


ELEMENTARY  ZOOLOGY 


muscles  in  the  walls  of  the  ampullae  the  fluid  in  the  cavity 
is  compressed,  thereby  forcing  the  tube-feet  out.  By  the 
contraction  of  muscles  in  the  tube-feet  they  are  again 
shortened  while  the  small  disk-like  terminal  sucker  clings 
to  some  firm  object.  In  this  way  the  animal  pulls  itself 


calcareous  spine  respiratory  caeca 


epithelium  of  the  body 
cavity ^ 


mesentery- 
pyloric  caecumr- 


lacral  ossicle 
ectodermal  covering* 


-ossicles 


— ampulla 


pedicellaria — U     /         /         ^tube  fool 
.radial ''canal     / 

radial  blood-vessel 

KIG.  19.  —  Semi-diagrammatic  figure  of  cross-section  of  the  ray  of  a  starfish, 

Asterias  sp. 

along  by  successive  "  steps."  This  entire  system,  called 
the  water-vascular  system,  is  characteristic  of  the  branch 
Echinodermata.  In  addition  to  the  fluid  in  the  water- 
vascular  system  there  is  yet  another  body-fluid,  the  peri- 
visceral  fluid,  which  bathes  all  of  the  tissues  and  fills  the 
body-cavity. 

TECHNICAL  NOTE. — Take  a  drop  of  the  perivisceral  fluid  from  a 
living  starfish  and  examine  under  high  power  of  microscope,  noting 
the  amoeboid  cells  it  contains. 

The  perivisceral  fluid  is  aerated  through  outpocketings 
oi  the  thin  body-wall  which  extend  outward  between  the 
calcareous  plates  of  the  body.  These  outpocketings  have 


'BRANCH  ECHINODERMATA :  STARFISHES,  ETC.         113 

already  been  mentioned  as  the  respiratory  caeca  (see 
p.  109).  Surrounding  the  stone  canal  is  a  thin  mem- 
branous tube,  and  within  it  and  by  the  side  of  the  stone 
canal  is  a  soft  tubular  sac.  The  function  of  these  organs 
is  not  certainly  known. 

Work  out  the  nervous  system;  note,  as  its  principal 
parts,  a  nerve-ring  about  the  mouth,  and  nerves  running 
from  this -ring  beneath  the  radial  canals  along  each  arm. 

Life-history  and  habits. — The  starfishes  are  all  marine 
forms.  They  hatch  from  eggs,  and  in  their  early  stages 
are  very  different  in  appearance  from  the  adults.  At  first 
they  are  bilaterally  symmetrical,  their  radial  symmetry 
being  acquired  later.  Thousands  of  eggs  and  sperm-cells 
are  extruded  into  the  sea-water,  where  fertilization  and 
development  take  place.  The  young  swim  freely  in  the 
open  sea,  feeding  on  microscopic  organisms,  and  then 
undergo  very  radical  changes  in  the  course  of  their 
development.  The  adults  are  for  the  most  part  carniv- 
orous, feeding  on  crabs,  snails,  and  the  like.  The  live 
prey  is  surrounded  by  the  extruded  stomach  which  secretes 
fluids  that  kill  it,  after  which  the  soft  parts  are  digested. 
(See  general  account  of  the  life-history  of  Echinoderms 
on  p.  1 19.) 

THE   SEA-URCHIN   (Strongylocentrotiis  sp.) 

External  Structure. — TECHNICAL  NOTE.— If  fresh  or  alco- 
holic specimens  or  even  the  dry  "tests"  of  the  sea-urchin  (fig.  20) 
are  to  be  had,  the  general  characteristics  of  the  external  structure 
can  be  made  out. 

How  does  the  external  surface  of  the  sea-urchin  differ 
from  that  of  the  starfish  ?  Can  you  find  the  very  long 
tube-feet  ?  Where  is  the  mouth-opening  ?  With  what  is 
it  surrounded  ?  Each  tooth  is  enclosed  in  a  calcareous 
framework.  The  whole  structure  is  known  as  " Aristotle's 
lantern. ' ' 


n4  ELEMENTARY  ZOOLOGY 

TECHNICAL  NOTE. — Remove  the  spines  from  the  underlying 
shell  or  test  (fig.  21)  and  wash  the  test  until  perfectly  clean,  or  place 
in  a  solution  of  lye  for  a  short  time  and  then  wash. 

Note,  the  characteristic  radial  symmetry  of  the  shell  or 
test.  Note  on  the  aboral  aspect,  diverging  from  the 
medial  anal  aperture,  five  double  rows  of  pores.  What 
are  these  for  ?  Each  of  the  five  divisions  set  with  pores 


FIG.  20. — A  sea-urchin,  Strongylocentrotus  franciscanns.     (From  specimen 
from  Bay  of  Monterey,  Calif. ) 

is  called  an  ambulacral  area,  while  the  intervening  seg- 
ments   which    support    the    long    spines    are    called    the 
inter  ambulacral  areas.      Note  on  the  aboral  surface,  sur- 
rounding the    median-placed  anal   aperture,   a    series    of 
small  plates.      Those  which  are  located  in  the  interambu-  ] 
lacral  areas  are  the  genital  plates.      Through  these  plates 
the  ducts  from  the  reproductive    organs    open  by  small 
pores.      Note  a  very  much  enlarged  plate  with  a  striated  j 
appearance.      This  is  the  madreporite,  which,  as    in  the  j 
starfish,  is  the  external  opening  of  the  stone  canal  and! 
water-vascular  system.      Note  the   small  ocular  plate   at  | 
the  tip  of  each  ambulacral  area.      The  ocular  plates  con-] 


BRANCH  ECHINODERMATA :  STARFISHES,  ETC.        115 

tain     small    pigment-cells    and     communicate    with     the 
nervous  system. 

From  a  general  inspection  of  the  sea-urchin's  shell  the 
Echinoderm  characteristics,  namely,  radial  symmetry  and 
the  presence  of  the  water-vascular  system,  are  readily 
seen.  While  at  first  glance  there  is  apparent  little 
similarity  between  the  starfish  and  sea-  urchin,  neverthe- 
less careful  examination  shows  that  the  two  animals  are 


FIG.    2i.— "Test"    of  Sea-urchin,    Strongylocentrotus  franciscanus,    with 
spines  removed.     (From  specimen.) 

alike  in  their  fundamental  structure.  Both  are  radially 
symmetrical.  The  position  of  the  anal  opening  makes 
both  starfish  and  sea-urchin  slightly  asymmetrical.  In 
both  the  madreporite  and  anus  are  on  the  aboral  side, 
while  the  mouth  is  centrally  located  on  the  oral  side! 
In  the  starfish  we  noted  five  ambulacral  areas,  one  on  the 
under  side  of  each  arm ;  similarly  we  find  five  in  the  sea- 
urchin.  In  both  cases  also  we  find  the  ocular  spots  at 
the  tips  of  the  ambulacral  areas.  The  genital  apertures 
are  situated  interradially  in  the  starfish.  In  the  sea- 
urchin  they  are  similarly  placed.  The  dissimilarity 
between  the  two  forms  is  largely  due  to  the  very  much 
developed  outer  spines  and  the  dorso-ventral  thickening 
of  the  disk  in  the  sea-urchin.  The  starfish  is  carnivorous, 
while  the  sea-urchin  lives  on  vegetable  matter  consisting 


n6  ELEMENTARY  ZOOLOGY 

for  the  most  part  of  green  algae  and  the  red  sea-weeds. 
Correlated  with  this  difference  in  food-habits  there  are 
certain  differences  in  the  structure  of  the  internal  organs. 
For  example,  the  alimentary  canal  in  the  sea-urchin  winds 
in  about  two  and  one-half  turns  within  the  body-cavity 
before  it  reaches  the  anus. 


OTHER    STARFISHES,    SEA-URCHINS,    SEA-CUCUMBERS, 

ETC. 

Without  exception  all  the  Echinoderms,  under  which 
term  are  included  the  starfishes,  sea-urchins,  brittle-stars, 
feather-stars,  and  sea-cucumbers,  live  in  the  ocean.  Some 
of  them,  the  starfishes  and  sea-urchins,  are  among  the 
most  common  and  familiar  animals  of  the  seashore.  Most 
of  them  are  not  fixed,  but  can  move  about  freely,  though 
slowly.  Some  of  the  feather-stars  are  fixed,  as  the 
sponges  and  polyps  are. 

Shape  and  organization  of  body. — The  body-shape  of 
the  Echinoderm  varies  from  the  flat,  rayed  body  of  the 
starfish  to  the  thick,  flattened  egg-shape  of  the  sea-urchin, 
the  melon-like  sac  of  the  sea-cucumber  and  the  delicate 
many-branched  head  of  the  sea-lily  sometimes  borne  on 
a  slender  stalk*  But  in  all  these  shapes  can  be  seen  more 
or  less  plainly  a  symmetrical,  radiate  arrangement  of  the 
parts  of  the  body.  The  Echinoderm  body  has  a  central 
portion  from  which  radiate  separate  arm  or  branch-like 
parts,  as  in  the  starfishes  and  sea-lilies,  or  about  which 
are  arranged  radiately  the  internal  body-parts,  although 
the  external  appearance  may  at  first  sight  give  no  plain 
indication  of  the  radiate  arrangement.  This  is  the  case 
with  the  sea-urchins  and  sea-cucumbers,  yet,  as  has  been 
seen  in  the  sea-urchin,  the  radiate  arrangement  can  be 
readily  perceived  by  closer  exanrnation  of  the  surface  of 
the  egg-  or  sac-like  body.  The  radiating  parts  of  the 


BRANCH  ECHINODERMATA :  STARFISHES,  ETC.          117 

body  are  usually  five.  In  the  body  of  an  Echinoderm 
can  be  usually  recognized  an  upper  or  dorsal  surface  and 
a  lower  or  ventral  surface.  The  mouth  is  usually  situated 
on  the  ventral  side  and  the  anal  opening  on  the  dorsal. 
Echinoderms  agree  also  in  having  a  calcareous  outer 
skeleton  or  body-wall  usually  in  the  condition  of  definitely- 
shaped  plates  or  spicules  fitted  either  movably  or  rigidly 
together.  This  outer  body-wall  or  exoskeleton  may  bear 
many  tubercles  or  spines.  These  spines  are  sometimes 
movable.  The  body-wall  of  the  sea-urchin  shows  very 
well  the  exoskeleton  composed  of  plates  on  which  are 
borne  movable  strong  spines. 

Structure  and  organs. — As  has  been  learned  from  the 
dissection  of  the  starfish,  the  Echinoderms  have  well- 
developed  systems  of  organs.  The  body-structure  in  its 
complex  organization  presents  a  marked  advance  beyond 
the  structural  condition  of  the  polyps  and  jellyfishes. 
There  is  a  well-organized  digestive  system  with  mouth, 
alimentary  canal,  and  anal  opening.  The  alimentary 
canal  is  either  a  simple  spiral  or  coiled  tube,  or  it  is  a  tube 
in  which  can  be  recognized  different  parts,  namely, 
oesophagus,  stomach,  intestine,  caeca,  and  special  glands 
secreting  digestive  fluids.  This  alimentary  canal  is  not, 
as  in  the  polyps,  simply  the  body-cavity,  but  it  is  an  in- 
closed tubular  cavity  lying  within  the  general  body-cavity. 
At  the  mouth-opening  there  is  in  some  Echinoderms, 
notably  the  sea-urchins,  a  strong  masticating  apparatus 
consisting  of  five  pointed  teeth  which  are  arranged  in  a 
circle  about  the  opening.  ["The  nervous  system  consists 
of  a  central  ring  around  the  oesophagus  or  mouth,  from 
which  branches  extend  into  the  radiately  arranged  arms 
or  regions  of  the  body.  There  is  no  brain  as  in  the 
higher  animals,  but  the  central  nerve-ring  is  composed  of 
both  nerve-cells  and  nerve-fibres  as  in  the  nerve-centres 
of  higher  forms.  Of  organs  of  special  sense  there  are 


n8  ELEMENTARY  ZOOLOGY 

special  tactile  or  touch  organs  in  all  the  Echinoderms, 
and  the  starfishes  have  very  simply  composed  eyes  or 
eye-like  organs  at  the  tips  of  the  rays. 

While  some  of  the  Echinoderms  breathe  simply  through 
the  outer  body-wall,  taking  up  by  osmosis  the  air  mixed 
with  the  water,  some  of  them  have  special,  though  very 
simple,  gill-like  respiratory  organs.  These  organs  con- 
sist of  small  membranous  sacs  which  are  either  pushed 
out  from  the  body  into  the  water,  or  lie  in  cavities  in  the 
body  to  which  the  water  has  access.  There  is  also  a  dis- 
tinct circulatory  system,  but  the  "  blood"  which  is 
carried  by  these  organs  and  which  fills  the  body-cavity 
consists  mainly  of  sea-water,  although  containing  a 
number  of  amoeboid  corpuscles  containing  a  brown  pig- 
ment. There  is  no  organ  really  corresponding  to  the 
heart  of  the  higher  animals.  There  are  distinct  organs 
for  the  production  of  the  germ  or  reproductive  cells.  The 
sexes  are  distinct  (except  in  a  few  species),  each  individual 
producing  only  sperm-cells  or  egg-cells,  but  the  organs 
or  glands  which  produce  the  germ-cells  are  very  much 
alike  in  both  sexes.  There  is  no  apparent  difference 
between  male  and  female  Eehinoderms  except  in  the 
character  or  rather  in  the  product  of  the  germ-cell  pro- 
ducing organs.  A  few  species  are  exceptions,  certain 
starfishes  showing  a  difference  in  color  between  males  and 
females. 

As  all  of  the  Echinoderms  except  some  of  the  feather- 
stars  can  move  about,  they  have  organs  of  locomotion, 
and  well-defined  muscles  for  the  movement  of  the  loco- 
motory  organs.  The  external  organs  of  locomotion,  the 
tube-feet  (in  the  sea-urchins  the  dermal  spines  aid  also  in 
locomotion),  are  parts  of  a  peculiar  system  of  organs 
characteristic  of  the  Echinoderms,  called  the  ambulacral 
or  the  water-vascular  system.  This  system  is  composed 
of  a  series  of  radial  tubular  vessels  which  rise  from  a  cen- 


BRANCH  ECH1NODERMATA :  STARFISHES,  ETC.         119 

tral  circular  or  ring  vessel  and  which  give  off  branches  to 
each  of  the  tube-feet.  The  water  from  the  outside  enters 
the  ambulacral  system  through  a  special  opening,  the 
madreporic  opening,  and  flowing  to  the  tube-feet  helps 
extend  them.  The  tube-feet  usually  have  a  tiny  sucking 
disk  at  the  tip,  and  by  means  of  them  the  Echinoderm 
can  cling  very  firmly  to  rocks. 

Development  and  life-history. — Differing  from  the 
sponges  and  the  polyps  and  jellyfishes,  the  reproduction 
of  the  Echinoderms  is  always  sexual ;  young  or  new  indi- 
viduals are  never  produced  by  budding,  or  in  any  other 
asexual  way.  The  new  individual  is  always  developed 
from  an  egg  produced  by  a  female  and  fertilized  by  the 
sperm  of  a  male.  The  eggs  are  usually  red  or  yellow, 
are  very  small  (about  ^  in.  in  diameter  in  certain 
starfishes),  and  are  fertilized  by  the  sperm-cells  of  the 
males  after  leaving  the  body  of  the  female.  That  is,  both 
sperm-cells  and  unfertilized  egg-cells  are  poured  out  into 
the  water  by  the  adults,  and  the  motile  sperm-cells  in 
some  way  find  and  fertilize  the  egg-cells. 

From  the  egg  there  hatches  a  tiny  larva  which  does 
not  at  all  resemble  the  parent  starfish  or  sea-urchin.  It 
is  an  active  free-swimming  creature,  more  or  less  ellip- 
soidal in  shape  and  provided  with  cilia  for  swimming. 
Soon  its  body  changes  form  and  assumes  a  very  curious 
shape  with  prominent  projections.  The  larvae  of  the 
various  kinds  of  Echinoderms,  as  the  starfishes,  sea- 
urchins,  sea-cucumbers,  etc.,  are  of  different  characteristic 
shapes.  The  naturalists  who  first  discovered  these  odd 
little  animals  did  not  associate  them  in  their  minds  with 
the  very  differently  shaped  starfishes  and  sea-urchins,  but 
believed  them  new  kinds  of  fully  developed  marine 
animals,  and  gave  them  names.  Thus  the  larvae  of  the 
starfishes  were  called  Bipinnaria,  the  larvae  of  the  sea- 
urchins  Pluteus,  and  so  on.  These  names  are  still  used 


120  ELEMENTARY  ZOOLOGY 

to  designate  the  larvae,  but  with  the  knowledge  that 
Bipinnaria  are  simply  young  starfishes,  and  that  a  Pluteus 
is  simply  a  young  sea-urchin.  From  these  larval  stages 
the  adult  or  fully  developed  starfish  or  sea-urchin  develops 
by  very  great  changes  or  metamorphoses.  The  Echino- 
derms  have  in  their  life-history  a  metamorphosis  as  strik- 
ing as  the  butterflies  and  moths,  which  are  crawling 
worm-like  caterpillars  in  their  young  or  larval  condition. 

Most  of  the  Echinoderms  have  the  power  of  regenerat- 
ing lost  parts.  That  is,  if  a  starfish  loses  an  arm  (ray) 
through  accident,  a  new  ray  will  grow  out  to  replace  the 
old.  And  this  power  of  regeneration  extends  so  far  in 
the  case  of  some  starfishes  that  if  very  badly  mutilated 
they  can  practically  regenerate  the  whole  body.  This 
amounts  to  a  kind  of  asexual  reproduction.  Some- 
species,  too,  have  the  peculiar  habit  of  self-mutilation. 
1  *  Many  brittle  stars  and  some  starfishes  when  removed 
from  the  water,  or  when  molested  in  dfny  way,  break  off 
portions  of  their  arms  piece  by  piece,  until,  it  may  be, 
the  whole  of  them  are  thrown  off  to  the  very  bases, 
leaving  the  central  disc  entirely  bereft  of  arms.  A  central 
disc  thus  partly  or  completely  deprived  of  its  arms  is 
capable  in  many  cases  of  developing  a  new  set;  and  a 
separated  arm  is  capable  in  many  cases  of  developing  a 
new  disc  and  a  completed  series  of  arms."  In  some  of 
the  sea-cucumbers  "it  is  the  internal  organs,  or  rather 
portions  of  them,  that  are  capable  of  being  thrown  off  and 
replaced,  the  oesophagus  ...  or  the  entire  alimentary 
canal,  being  ejected  from  the  body  by  strong  contrac- 
tions of  the  muscular  fibres  of  the  body-wall,  and  in 
some  cases,  at  least,  afterwards  becoming  completely 
renewed. " 

Classification. — The  Echinodermata  are  divided  into 
five  classes,  viz.,  the  Asteroidea  or  starfishes,  "free 
Echinoderms  with  star-shaped  or  pentagonal  body,  in 


BRANCH  ECHINODERMATA :  STARFISHES,  ETC.          1 21 

which  a  central  disc  and  usually  five  arms  are  more  or 
less  readily  distinguishable,  the  arms  being  hollow  and 
each  containing  a  prolongation  of  the  body-cavity  and 
contained  organs";  the  OgJiLurojdea,  or  brittle-stars, 
"star-shaped  free  Echinoderms,  with  a  central  disc  and 
five  arms,  which  are  more  sharply  marked  off  from  the 
disc  than  in  the  Asteroidea  and  which  contain  no  spacious 
prolongations  of  the  body-cavity  ' ' ;  the  Echinoidea,  or 
sea-urchins,  ' '  free  Echinoderms  with  globular,  heart- 
shaped,  or  disc-shaped  body  enclosed  in  a  shell  or  corona 
of  close-fitting,  firmly  united  calcareous  plates";  the 
Holuthuroidea,  or  sea-cucumbers,  "free  Kchinoderms 
with  elongated  cylindrical  or  five-sided  body,  .  .  .  with  a 
circlet  of  large  oral  tentacles  ";  and  the  Crinoic]ea,  or 
feather-stars,  * '  temporarily  or  permanently  stalked  Echi- 
noderms with  star-shaped  body,  consisting  of  a  central  disc, 
and  a  series  of  five  bifurcate  or  more  completely  branched 
arms,  bordered  with  pinnules." 

Starfishes  (Asteroidea). — The  starfishes  feed  on  other 
marine  animals,  especially  shell-fish  and  crabs.  They 
are  also  reputed  to  destroy  young  fish.  By  means  of  their 
sucking-tubes,  or  tube-feet  with  sucker  tips,  they  can 
seize  and  hold  their  prey  firmly.  They  do  much  injury 
to  oyster-beds  by  attacking  and  devouring  the  oysters. 
When  attacking  prey  too  large  to  be  taken  into  the  mouth 
the  starfish  everts  its  stomach  over  the  prey  and  devours 
it.  The  stomach  is  afterward  drawn  back  into  the  body- 
cavity  by  special  muscles. 

Starfishes  vary  much  in  size,  color  and  general  appear- 
ance, although  all  are  readily  recognizable  as  starfishes 
(fig.  22).  The  number  of  arms  or  rays  varies  from  five 
to  thirty  or  more  in  different  species;  some  have  the 
interradial  spaces  filled  out  nearly  to  the  tips  of  the  rays, 
making  the  animal  simply  a  pentagonal  disc.  In  size 
starfishes  vary  from  a  fraction  of  an  inch  in  diameter  to 


122 


ELEMENTARY  ZOOLOGY 


three  feet;  in  color  they  are  yellow  or  red  or  brown  or 
purple. 

Brittle-stars  (Ophiuroidea) .  —  The  brittle-stars,  or  ser- 


>.\>'ttJ&> 

*&&$ 


":^r5-^r> 


pent-stars  (fig.  22)  as 
they  are  also  called, 
resemble  the  starfishes 
in  external  appearance, 
that  is,  they  are  flat  and 

FIG.  22.— A  group  of  Echinoderms;  the  composed    of  a    Central 

upper  one.  a  starfish,  Asterina  mineata  •,•           .  ,          ,. 

the  one  at -the  right  a  starfish,  Asterias  dlSC  Wltn  radiating  arms 
ocracia,    at   the    left   a    brittle-star,   spe- 


(always  five  in  number, 
although      each      arm 


,  - 
cies unknown,  and  at  bottom  two  sea- 
urch  ins,  Strongylocentrotn*.  franciscanus. 
(From  living  specimens  in  a  tide-pool  on 
the  Bay  of  Monterey,  California.) 

branched).   The  central 

disc  is  always   sharply  distinguished  from  the  arms,  and 
the    arms    are  usually    slender  and  more    or  less    cylin- 


BRANCH  ECHINODERMATA :  STARFISHES,  ETC.         123 

drical.  The  distinguishing  difference  between  the  brittle- 
stars  and  the  starfishes  is  that  the  body-cavity  and  the 
stomach  which  extend  out  into  the  arms  in  the  star- 
fishes are  in  the  brittle-stars  limited  to  the  central  disc,  or 
to  the  disc  and  bases  of  the  arms.  The  tube-feet  also 
have  no  suckers  at  the  tips.  More  than  700  species  of 
brittle-stars  are  known.  They  feed  on  marirjfe  shell-fish, 
crabs  and  worms.  /'• 

Sea-urchins  (Echinoidea). — The  sea-urchins  (figs.  20,  2 1 
and  22)  of  which  more  than  300  species  are  known,  have 
no  arms  or  rays,  and  they  are  usually  not  flat  like  the  star- 
fishes but  globular,  with  poles  more  or  less  flattened.  As 
has  been  noted  in  the  examination  of  the  body-wall  or 
* '  shell, ' '  the  radiate  character  of  the  body  is  shown  by  the 
five  radiating  zones  of  tube-feet.  The  mouth,  with  its  five 
strong  "teeth,"  is  on  the  ventral  surface,  and  the  anal 
opening  and  madreporic  opening  are  on  the  dorsal  sur- 
face. The  calcareous  plates  (seen  distinctly  in  a  specimen 
from  which  the  spines  have  been  removed)  which  consti- 
tute the  firm  part  of  the  body- wall,  are  more  or  less 
pentagonal  in  shape  and  are  usually  firmly  united  at  the 
edges.  The  spines  which  are  so  characteristic  of  the 
sea-urchins  vary  much  in  size  and  number  and  firmness, 
but  are  present  in  some  form  on  all  of  them. 

\Yhile  most  of  the  sea-urchins  live  near  the  shore, 
being  very  common  in  tide-pools,  some  live  only  on  the 
bottom  of  the  ocean  at  great  depths.  Their  food  consists 
of  small  marine  animals  and  of  bits  of  organic  matter 
which  they  collect  from  the  sand  and  debris  of  the  ocean 
floor.  Many  of  the  sea-urchins  are  gregarious,  living 
together  in  great  numbers.  Some  have  the  habit  of 
boring  into  the  rocks  of  the  shore  between  tide-lines.  I 
have  seen  thousands  of  small  beautifully  colored  purple 
sea-urchins  lying  each  in  a  spherical  pit  or  hole  in  hard 
conglomerate  rock  on  the  California  coast.  How  they 


124  ELEMENTARY  ZOOLOGY 

are  enabled  to  bore  these  holes  is  not  yet  known. 
There  is  great  variety  in  size  and  color  among  the  sea- 
urchins.  The  colors  are  brown,  olive,  purple  red,  greenish 
blue,  etc. 

A  few  kinds  of  sea-urchins  have  a  flexible  shell  or  test. 
The  Challenger  expedition  dredged  up  from  sea-bottom 
some  sea-urchins,  and  when  placed  on  the  ship's  deck 
<4the  test  moved  and  shrank  from  touch  when  handled, 
and  felt  like  a  starfish. ' '  The  cake-urchins  or  sand- 
dollars  are  sea-urchins  having  a  very  flat  body  with  short 
spines.  They  lie  buried  in  the  sand,  and  are  often  very 
brightly  colored.  Their  hollow  bleached  tests  with  the 
spines  all  rubbed  off  are  common  on  the  sands  of  both 
the  Atlantic  and  Pacific  coasts. 

Sea-cucumbers  (Holothuroidea). — The  sea-cucumbers 
(fig.  23)  show  at  first  glance  little  resemblance  to  the 
other  radiate  animals.  The  body  is  an  elongate,  sub- 
cylindrical  sac,  resembling  a  thick  worm  or  sausage  or 
cucumber  in  shape.  At  one  end  it  bears  a  group  of 
branched  tentacles  which  are  set  in  a  ring  around  the 
mouth-opening.  The  body-wall  is  muscular  and  leathery, 
but  contains  many  small  separated  calcareous  spicules. 
There  are  usually  five  longitudinal  rows  of  tube-feet.  In 
some  species,  however,  tube  feet  are  wholly  wanting;  in 
others  they  are  scattered  over  the  surface. 

Although  there  are  known  about  five  hundred  species 
of  sea-cucumber's  many  of  which  live  along  the  shores, 
they  are  much  less  familiar  to  us  than  the  starfishes  and 
sea-urchins.  They  usually  rest  buried  in  the  sand  by  day, 
feeding  at  night.  Some  of  them  attain  a  large  size.  A 
great  orange-red  species  of  the  genus  Cuciimaria,  which 
is  found  in  the  Bay  of  Monterey,  California,  is  three  feet 
long. 

The  people  of  some  nations  use  sea-cucumbers  as  food. 
They  are  called  "  trepang  "  in  the  orient.  The  trade  of 


BRANCH  ECHINODERMA TA  :  S TARFISHES,  ETC.          125 

preparing  the  trepang  is  almost  entirely  in  the  hands  of 
the    Malays,   and    every   year    large  fleets  set  sail  from 


FIG.  23. — A  sea-cucumber,  Pentacta  frondosa.     (After  Emerton.) 

Macassar  and  the   Philippines  to  the  south  seas  to  catch 
sea-cucumbers. 

Feather-stars  (Crinoidea) . — The  feather-stars  or  sea- 
lilies  or  crinoids  (fig.  24),  as  they  are  variously  called,  differ 
from  the  other  Echinoderms  in  having  the  mouth  on  the 
upper  side  of  the  central  disc,  and  in  the  fact  that  all  of 
the  species  are  fixed,  either  permanently  or  for  a  part  of 
their  life,  being  attached  to  rocks  on  the  sea-bottom  by 
a  longer  or  shorter  stalk  which  is  composed  of  a  series  of 
rings  or  segments.  The  central  disc  is  small  and  the 


126 


ELEMENTARY  ZOOLOGY 


radiating  arms  are  long,  slender,  sometimes  repeatedly 
branched,  and  all  the  branches  bear  fine  lateral  projec- 
tions called  pinnulae.  Most  of  the  feather-stars  live  in 
deep  water  and  are  thus  only  seen  after  being  dredged 
up.  They  feed  on  small  crab-like  animals,  and  on  the 
marine  unicellular  animals  and  plants. 


FIG.  24.  —A  crinoid  or  feather-star,  Pentacrinus  sp.     (After  Brehm.) 


CHAPTER    XIX 
BRANCH    VERMES:*    THE    WORMS 

THE   EARTHWORM  (Lumbricus  sp.). 

TECHNICAL  NOTE. — Obtain  live  earthworms  of  large  size,  killing 
some  in  30^  alcohol  and  hardening  and  preserving  them  in  8o#  alco- 
hol, and  bringing  others  alive  to  the  laboratory.  The  worms  may 
be  found  during  the  daytime  by  digging,  or  at  night  by  searching 
with  a  lantern.  They  often  come  above  ground  in  the  daytime 
after  a  heavy  rain.  Live  specimens  may  be  kept  in  the  laboratory 
in  flower-pots  filled  with  soil.  "  They  may  be  fed  on  bits  of  raw 
meat,  preferably  fat,  bits  of  onion,  celery,  cabbage,  etc.,  thrown  on 
the  soil." 

External  structure  (fig.  25). — Examine  the  external 
structure  of  live  and  dead  specimens.  Which  is  the  ventral 
and  which  the  dorsal  surface  ?  Which  the  anterior  and 
which  the  posterior  end  ?  Note  the  segmented  condition 
of  the  body;  the  number  of  segments  or  somites,  and  their 
relative  size  and  shape.  Note  absence  of  appendages  such 
as  limbs  and  the  presence  of  locomotor  seta  (short  bristles). 
How  many  setae  are  there  on  each  segment  and  what  is 
their  disposition  ?  The  moutJi  is  covered  by  a  dorsal 
projection  called  the  prostomium.  The  anal  opening  is 
situated  in  the  posterior  segment  of  the  body.  The  broad 
thickened  ring  or  girdle  including  several  segments  near 

*  The  author  recognizes  the  untenability  of  the  group  Vermes  as  a  group 
co-ordinate  with  the  other  branches  of  the  animal  kingdom,  and  that 
"Vermes"  has  been  discarded  in  modern  text-books.  But  because  of  the 
very  scant  consideration  whic^i  can  he  given  the  various  kinds  of  worm  like 
animals  the  course  of  the  older  text-books  will  be  followed,  and  all  of  the 
worm-like  animals,  as  far  as  referred  to  in  ihis  book,  be  considered  under 
the  group  name  Vermes. 

127 


128 


ELEMENTARY  ZOOLOGY 


retractor  and  protractor 
muscles  of  the  phq/ry 

cesophageal  pouches- 
reproductive  organs = 


reproductive  organs  — •- 


:erebral  ganglion 


pharynx 
^esophagus 


JTIG.  25.— Dissection  of  the  earthworm,  Lumbricus  sp. 


BRANCH   YERMES:    THE   IVOR  MS  129 

the  anterior  end  of  the  body  is  the  clitellum,  a—gkrtidular 
structure  which  secretes  the  cases  in  which  the  'eggs  are 
laid.  On  the  ventral  surface  of  the  fourteenth  and 
fifteenth  segments  (in  most  species)  are  two  pairs  of  small 
pores ;  two  other  pairs  of  small  openings  (usually  difficult 
to  find),  one  between  segments  9  and  10,  and  one  between 
segments  10  and  11,  are  present.  All  these  are  the 
external  openings  of  the  reproductive  organs. 

Make  drawings  showing  the  external  structure  of  the 
earthworm. 

Examine  a  live  specimen  placed  on  moist  paper  or 
wood.  Note  the  characteristics  of  its  locomotion,  and 
the  movements  of  its  body-parts.  How  do  tfie  setae  aid 
in  locomotion  ? 

Internal   structure    (figs.    25,   26   and   28).— TECHNICAL 

NOTE. — With  a  fine-pointed  pair  of  scissors  make  a  dorsal  median 
incision,  not  too  deep,  behind  the  clitellum  and  cut  forward  as  far 
as  the  first  segment.  Put  the  specimen  into  dissecting-dish,  care- 
fully pin  back  the  edges  of  the  cut  and  cover  with  clear  water  or, 
better,  50^  alcohol. 

Note  the  long  body-cavity  divided  by  the  thin  septa 
which  have  been  torn  away  for  the  most  part  by  the 
pinning  process.  Note  the  thin  transparent  covering  of 
the  body,  the  cuticle.  Just  beneath  this  note  a  less  trans- 
parent layer,  the  epidermis,  and  underneath  this  a  layer 
of  muscles.  The  muscular  layer  is  made  up  of  two 
clearly  recognizable  sets,  an  outer  circular  layer  and  an 
inner  longitudinal  layer  the  fibres  of  which  are  continuous 
with  the  septa. 

Note,  as  the  most  conspicuous  internal  organ,  the  long 
alimentary  canal,  of  which  a  number  of  distinct  parts  may 
be  recognized.  Most  anteriorly  is  a  muscular  pJiarynx, 
which  is  followed  by  a  narrow  oesophagus,  leading  directly 
into  the  thin-walled  crop;  next  comes  the  muscular 


130  ELEMENTARY  ZOOLOGY 

gizzard,  and  next  the  intestine  wtyich  opens  externally  in 
the  terminal  segment  through  the  anus.  The  anterior  end 
of  the  alimentary  canal  is  more  or  less  protrusible,  while 
the  posterior  portion  is  held  more  firmly  in  place  by  the 
septa  which  act  as  mesenteries.  Surrounding  the  narrow 
oesophagus  are  the  reproductive  organs,  three  pairs  of 
large  white  bodies  and  two  pairs  of  smaller  sacs. 

Note  the  dorsal  blood-vessel  lying  along  the  dorsal 
surface  of  the  alimentary  canal,  from  the  anterior  por- 
tion of  which  arise  several  circumcesophageal  rings  or 
"hearts."  These  hearts  are  contractile  and  serve  to 
keep  the  blood  in  motion  tfirough  the  blood-ve-ssels  (see 
later).  In  the  most  anterior  of  the  body  segments  note 
the  pear-shaped  brain  or  cerebral  ganglion. 

TECHNICAL  NOTE. — Lilt  carefully  to  right  and  left  the  repro- 
ductive organs,  thus  exposing  the  oesophagus. 

Note  three  pairs  of  bag-like  structures  projecting  from 
the  oesophagus.  The  front  pair  is  the  oesopJiageal  pouches; 
the  next  two  pairs  are  the  oesopJiageal  or  calciferous 
glands.  They  communicate  with  the  alimentary  canal, 
and  their  secretion  is  a  milky  calcareous  fluid. 

Make  a  drawing  that  will  show  all  the  parts  so  far 
studied. 

TECHNICAL  NOTE.— Cut  transversely  through  the  alimentary 
canal  in  the  region  of  the  clitellum  and  carefully  dissect  the  anterior 
portion  of  the  canal  away  from  the  surrounding  organs. 

Note  the  dorsal  fold  of  the  intestine,  typJilosole,  ex- 
tending into  the  lumen.  This  fold  gives  a  greater  surface 
for  digestion,  and  in  it  are  a  great  many  hepatic  or  special 
digestive  cells.  The  entire  alimentary  canal  is  lined  with 
epithelium.  Observe  just  beneath  the  alimentary  canal 
the  ventral  blood-vessel,  and  still  beneath  this  blood- 
vessel the  ventral  nerve-cord.  There  is  a  slight  swelling 
on  the  nerve-cord  in  each  segment  of  the  body.  These 


BRANCH   YERMES:    THE   WORMS  I31 

swellings  are  the  ganglia.  How  many  pairs  of  nerves 
are  given  off  from  each  ganglion  ?  Observe  in  each  seg- 
ment, posterior  to  the  first  three  or  four,  the  successive 


Dorsal  blood  vessel 


lyphlosole 


•intestine 


nepkrostome 

ventral  nerve  cord 

FIG.  26. — Dissection  to  show  alimentary  canal  in  section   and  nephridia 
of  earthworm. 

pairs  of  convoluted  tubes,  the  nephridia,  or  organs  of 
excretion.  Each  nephridium  opens  internally  through  a 
ciliated  funnel,  the  nepJirostome,  within  the  body-cavity, 
while  it  opens  externally  by  a  small  excretory  pore 
between  the  setae  on  the  ventral  surface  of  the  segment 
behind  that  in  which  the  nephridium  chiefly  lies.  The 
function  of  the  nephridia  is  to  carry  off  waste  matter 
from  the  fluid  which  fills  the  body-cavity. 

Trace  the  ventral  nerve-cord  forward  to  its  connection 
with  the  cerebral  ganglion.  Note  the  threat  nerve-ring 
or  circumccsophageal  collar  connecting  the  ventral  cord 
with  the  brain. 

Make  a  drawing  of  the  nervous  system  showing  its 
relation  to  other  organs. 

Life- history  and  habits.— The  earthworm  lives  in  soft 
moist  soil  which  is  rich  in  organic  matter.  Its  food  is 


I32 


ELEMENTARY  ZOOLOGY 


taken  into  the  mouth  mixed  with  dirt  and  sand.  As  this 
mixture  passes  through  the  long  alimentary  canal  the 
organic  particles  are  taken  up  and  digested.  As  we  have 
already  seen,  there  are  in  each  worm  two  sets  of  reproduc- 
tive glands,  namely,  male  and  female  organs.  Each 
earthworm  produces  both  egg-cells  and  sperm-cells,  but 

nephridium  dorsal  blood  vessel 

\     hepatic  cells  I 
\        \  I  longitudinal  muscle 

\        \  /i    Circular  muscle  fibres 

'  epidermis 
V  V  ^  \  \^      ^^^cuiicle 


',  !   \  nerve* cor d\ 

lephndipore  !  nephrostome     \ 

*  D 

body  cavily 


typhlosole 


ventral  vessel 


FIG.  28. — Cross-section  of  earthworm. 


the  sperm-cells  of  one  worm  are  not  used  to  fertilize  the 
eggs  of  the  individual  producing  them.  When  the  eggs 
are  ready  to  be  discharged  from  the  bod)/,  the  clitellum 
becomes  very  much  swollen  and  its  glands  begin  an  active 
secretion  which  hardens  and  forms  a  collar-like  structure 
about  the  body  of  the  worm.  As  this  collar  moves 
forward  toward  the  anterior  end  of  the  body  it  collects  the 
eggs  and  also  the  sperm-cells  previously  received  from 


BRANCH   VERMES:    THE   WORMS  133 

another  worm,  and  finally  slips  off  the  head  end  of  the 
animal.  The  entire  structure  with  the  contained  eggs 
and  sperm-cells  as  it  passes  off  from  the  body  becomes 
closed  at  both  ends,  thus  forming  a  horny  capsule  which 
lies  in  the  earth  until  the  young  worms  emerge.  Only  a 
part  of  the  eggs  develop  in  each  capsule,  the  rest  being 
used  as  food  for  the  growing  young.  The  young  earth- 
worms, though  of  very  small  size,  are  fully  formed  before 
they  leave  the  egg-capsule.  Earthworms  are  more  or  less 
gregarious,  large  numbers  often  being  found  together. 

For  an  interesting  account  of  the  habits  of  earthworms 
see  Darwin's-  "  The  Formation  of  Vegetable  Mold." 


OTHER    WORMS. 

The  branch  Vermes  comprises  so  large  a  number  of 
kinds  of  animals  presenting  such  great  differences  in  struc- 
ture and  habit  that  it  is  impossible  to  give  a  brief  state- 
ment in  general  or  summary  terms  of  their  external 
body-characters,  of  the  structural  and  functional  condition 
of  their  various  organs  and  systems  of  organs,  and  of  the 
course  of  their  development  and  life-history  as  has  been 
done  for  the  preceding  branches.  Many  zoologists, 
indeed,  do  not  include  all  the  worms  or  worm-like  animals 
in  one  branch,  but  consider  them  to  form  several  distinct 
branches. 

In  certain  very  general  characters  all  of  the  animals 

which  compose  the   branch    Vermes  do  agree.      All,  or 

/  nearly  all,   have  an    elongate  body  which   is  bilaterally 

\   symmetrical,   that   is,    which   could  be  cut  by  a  median 

longitudinal  cutting  in  two  similar  halves.      In   most  of 

J  them  also  the  body  is  composed  of  a  number  of  successive 

\  segments  or  somites  which  are  more  or  less  alike.      This 

kind  of  segmented  or  articulated  body  is  also  possessed  by 


13  J  ELEMENTARY  ZOOLOGY 

the  insects  and  crabs.  Almost  all  of  the  worms  have  the 
power  of  locomotion ;  usually  that  of  crawling.  For 
this  crawling  they  do  not  have  legs  composed  of  separate 
segments  or  joints  as  do  the  higher  articulated  animals, 


FIG.  29. — A  group  of  marine  worms;  at  the  left  a  gephyrean,  Dendrostomum 
cronjhelmi,  the  upper  right-hand  one  a  nereid,  Nereis  sp.,  the  lower 
right-hand  one,  Polynoe  brevisetosa.  (From  living  specimens  in  a 
tide-pool  on  the  Bay  of  Monterey,  California.) 


the  crabs  and  insects,  but  either  have  fleshy  unjointed 
legs,  or  various  kinds  of  bristles  or  spines,  or  suckers,  or 
even  no  external  organs  of  locomotion  at  all.  As  regards 
their  internal  structure  they  have  well-organized  systems 
of  organs,  which  show  great  variety  in  character  and 
degree  of  complexity.  The  special  sense-organs  are 
usually  of  simple  character  and  low  degree  of  functional 
•development.  Reproduction  occurs  both  sexually  and 
asexually;  in  some  species  the  sexes  are  distinct,  while 
in  others  both  sperm-cells  and  egg-cells  are  produced  by 
the  same  individual.  Asexual  reproduction  is  by  budding 
or  by  a  kind  of  simple  division  or  fission.  The  worms 
live  either  in  salt  or  fresh  water,  or  in  moist,  muddy  or 
slimy  places  or  as  parasites  in  the  bodies  of  other  animals 
or  in  plants.  While  most  worms  feed  on  animal  sub- 


BRANCH   VERMES:   THE   WORMS  1 35 

stance  either  living  or  dead,  some  feed  on  living  or 
decaying  plant  matter. 

Classification.  —  There  is  great  lack  of  agreement 
among  zoologists  in  the  matter  of  the  classification  of  the 
worms.  Not  only  are  the  various  groups  which  by  some 
are  called  classes  held  by  others  to  be  distinct  branches, 
co-ordinate  in  rank  with  the  Echinodermata,  Ccelenterata, 
etc.,  but  the  limits  of  these  groups  are  also  constantly 
called  in  question.  It  will  require  a  great  deal  better 
knowledge  of  the  structure  and  life-history  of  these  diverse 
animals  before  the  matter  of  their  classification  is  satisfac- 
torily settled.  We  shall  consider  briefly  four  of  the 
various  groups  (which  we  may  consider  as  classes)  which 
include  worms  either  specially  familiar  to  us  or  of  special 
interest  or  importance.  One  or  two  examples  of  each 
group  (the  groups  being  selected  primarily  because  of  the 
examples)  will  be  described  in  some  detail.  By  this 
means  we  may  get  an  idea  of  the  extremely  diverse  char- 
acter of  the  animals  which  are  included  in  the  heteroge- 
neous branch  Vermes. 

Earthworms  and  leeches  (Oligochaetae) . — The  various 
species  of  earthworms,  an  example  of  which  has  been 
studied  are  found  in  all  parts  of  the  world;  they  occur  in 
Siberia  and  south  to  the  Kerguelen  Islands.  They  are 
absent  from  desert  or  arid  regions,  and  some  can  live 
indifferently  either  in  soil  or  in  water.  Some  near  allies 
ot  the  earthworms  are  aquatic,  living  in  fresh  or  brackish 
water,  some  in  salt  water  near  the  shore.  In  size  earth- 
worms vary  from  I  mm.  (fa  in.)  to  2  metres  (2^  yds.)  in 
length.  All  show  the  distinct  segmentation  of  the  body 
noticeable  in  the  common  earthworm  already  studied. 

The  leeches,  some  of  which  are  familiar  animals,  are 
closely  related  to  the  earthworms,  although  at  first  glance 
the  similarity  in  structure  is  not  very  noticeable. 


I3  ELEMENTARY  ZOOLOGY 

TECHNICAL  NOTE. — Some  common  water-leeches,  alive  or  pre- 
served in  alcohol,  should  be  examined  by  the  class.  The  animals 
are  not  unfamiliar  to  boys  who  "go  in  swimming"  in  the  small 
streams  of  the  country.  The  body  of  a  leech  should  be  examined 
carefully,  and  drawings  of  it  showing  the  external  structural  charac- 
ters should  be  made. 

The  body  of  a  leech  is  flattened  dorso-ventrally,  instead 
of  being  cylindrical  as  in  the  earthworm,  and  tapers  at 
both  ends.  In  the  live  animal  the  body  can  be  greatly 
elongated  and  narrowed  or  much  shortened  and  broad- 
ened. It  is  composed  of  many  segments  (not  as  many 
as  there  are  cross-lines  however;  each  segment  is  trans- 
versely annulated),  and  bears  at  each  end  on  the  ventral 
surface  a  sucker,  the  one  at  the  posterior  end  being  the 
larger.  These  suckers  enable  the  leech  to  cling  firmly 
to  other  animals.  The  mouth  is  at  the  front  end  of  the 
body  on  the  ventral  surface  and  is  provided  with  sharp 
jaws.  Leeches  live  mostly  on  the  blood  of  other  animals 
which  they  suck  from  the  body.  The  common  leech 
"fastens  itself  upon  its  victim  by  means  of  its  suckers, 
then  cuts  the  skin,  fastens  its  oral  sucker  over  the  wound 
and  pumps  away  until  it  has  completely  gorged  itself  with 
blood,  distending  enormously  its  elastic  body,  when  it 
loosens  its  hold  and  drops  off. ' '  Its  biting  and  sucking 
cause  very  little  pain,  and  in  olden  days  physicians  used 
the  leeches  when  they  wanted  to  "  bleed  "  a  person.  A 
common  European  species  of  leech  much  used  for  this 
purpose  is  known  as  the  "medicinal  leech."  All 
leeches  are  hermaphroditic,  that  is,  the  sexes  are  not  dis- 
tinct, but  each  individual  produces  both  sperm-cells  and 
egg-cells.  Most  of  the  leeches  lay  their  eggs  in  small 
packets  or  cocoons.  This  cocoon  is  dropped  in  soil  on  the 
banks  of  a  pond  or  stream  so  that  the  young  may  have  a 
moist  but  not  too  wet  environment.  The  young  issue 
from  the  eggs  in  four  or  five  weeks,  but  they  grow  very 


BRANCH   HERMES:   THE   WORMS  137' 

slowly  and  it  is  several  years  before  they  attain  their  full 
size.  Leeches  are  long-lived  animals,  some  being  said 
to  live  for  twenty  years. 

Flat  worms  (Platyhelminthes).  —  TECHNICAL  NOTE.— 
Collect  some  live  fresh-water  planarians  (see  fig.  30),  which  are  to  be 
found  on  the  muddy  bottom  of  most  fresh-water  ponds,  and  examine 
them  while  alive  in  watch-glasses  of  water.  Make  drawings  show- 
ing the  external  appearance,  and  as  much  of  the  internal  anatomy 
as  can  be  seen.  The  branching  alimentary  canal  can  be  seen  in 
more  or  less  detail,  and  with  higher  power  of  the  microscope  parts 
of  the  nervous  system  can  be  seen  also.  Have  also  a  tapeworm 
preserved  in  alcohol  or  formalin  to  show  the  very  flat  and  many- 
segmented  body. 

The  flatworms  include  a  large  number  of  forms  which 
vary  much  in  shape  and  habits.  They  are  all,  however, 


FIG.  30. — A  fresh  water  planarian,  Planaria  sp.    (From  a  living  specimen.) 

characteristically  flat;  in  some  this  condition  is  very 
marked.  Some  are  active  free-living  animals,  as  the 
planarians  (figs.  30  and  31),  while  many  live  as  parasites 
in  the  alimentary  canal  of  other  animals,  as  do  the  sheep- 
fluke  and  the  tapeworms. 

The  fresh- water  planarians  (fig.  30),  which  live  com- 
monly in  the  mud  of  the  bottom  of  ponds,  are  small, 
being  less  than  half  an  inch  long.  They  are  very  thin 
and  rather  broad,  tapering  from  in  front  backwards.  On 
the  upper  surface  near  the  front  they  have  a  pair  of  eyes ; 
the  noouth  is  on  the  under  surface  a  little  behind  the 
middle  of  the  body.  The  alimentary  canal  is  composed 
of  three  main  branches,  each  with  numerous  small  side 
branches.  One  main  branch  runs  forward  from  the 
mouth,  and  the  other  two  run  backwards,  one  on  each 
side  of  the  body.  There  is  no  anal  opening,  and  the 


138  ELEMENTARY  ZOOLOGY 

alimentary  canal  thus  forms  a  system  of  fine  branches 
closed  at  the  tips,  and  extending  all  through  the  body. 
The  nervous  system  is  composed  of  a  ganglion  or  brain 
in  the  front  end  of  the  body  from  which  two  main  branches 
extend  back  throughout  its  whole  length.  From  these 
main  longitudinal  branches  arise  many  fine  lateral 
branches. 

Of  the  parasitic  flatworms  the  tapeworms  are  the  best 
known.      There   are    numerous    species    of    them,    all   of 


FIG.  31. — A  marine  planarian,    Leptoplana   californica.     (From    a   living 

specimen.) 

which  live  in  the  bodies  of  vertebrate  animals.  In  the 
adult  or  fully  developed  stage  the  tapeworms  live  in  the 
alimentary  canal,  holding  on  to  its  inner  surface  by  hook- 
like  clinging  organs  and  being  nourished  by  the  already 
digested  food  by  which  they  are  bathed.  In  the  young 
or  larval  stage  tapeworms  live  in  other  parts  of  the  body 
of  the  host,  and  usually,  indeed,  in  other  hosts  not  of  the 
same  species  as  the  host  of  the  adult  worm. 


BRANCH   YERMES:    THE   WORMS  139 

The  common  tapeworm  of  man,  Tcenia  solinm  (there 
are  several  other  species  of  Tcenia  which  infest 
man,  but  solium  is  the  common  one),  may  serve  as  an 
example  of  the  group.  In  the  adult  condition  its  body, 
which  is  found  attached  to  the  inner  wall  of  the  intestine, 
is  like  a  long  narrqw  ribbon :  it  may  be  two  or  three 
metres  long.  It  is  attached  by  one  end,  the  head,  which 
is  very  small  and  provided  with  a  score  of  fine  hooks. 
Behind  the  head  the  thin  ribbon-like  body  grows  wider. 
The  body  is  composed  of  many  (about  850)  joints  called 
proglottids.  There  is  no  mouth  or  alimentary  canal,  the 
liquid  food  being  simply  taken  in  through  the  skin.  Each 
proglottid  produces  both  sperm-cells  and  egg-cells ;  one 
by  one  these  proglottids  or  joints  with  their  supply  of 
fertilized  eggs  break  off  and  pass  from  the  alimentary 
canal  with  the  excreta.  If  now  one  of  these  escaped 
proglottids  or  the  eggs  from  it  are  eaten  by  a  pig,  the 
embryos  issue  from  the  eggs  in  the  alimentary  canal  of 
the  pig,  bore  through  the  walls  of  the  canal  and  lodge  in 
the  muscles.  Here  they  increase  greatly  in  size  and 
develop  into  a  sort  of  rounded  sac  filled  with  liquid.  If 
the  flesh  of  the  pig  be  eaten  by  a  man,  without  its  being 
first  cooked  sufficiently  to  kill  the  larval  sac-like  tape- 
worms, these  young  tapeworms  lodge  in  the  alimentary 
canal  of  the  man  and  develop  and  grow  into  the  long 
ribbon-like  many-jointed  adult  stage. 

The  life-history  of  the  other  tapeworms  which  infest 
the  various  vertebrate  animals  is  of  this  general  type. 
There  is  almost  always  an  alternation  of  hosts,  the  larval 
tapeworm  living  in  a  so-called  intermediate  host,  and  the 
adult  in  a  final  host.  Of  the  domestic  animals  the  dog 
is  the  most  frequently  attacked.  At  least  ten  different 
species  of  tapeworms  have  been  found  in  the  dog.  The 
intermediate  hosts  of  these  dog  tapeworms  include 
rabbits,  sheep,  mice,  etc.  Some  of  the  domestic  fowl, 


140 


ELEMENTARY  ZOOLOGY 


ducks,  geese  and  chickens,  for  instance,  are  also  infested 
by  tapeworms,  and  the  intermediate  hosts  in  these  cases 
are  usually  insects  or  small  aquatic  crustaceans  like  the 
familiar  Cyclops. 

Roundworms  (Nemathelminthes) . — TECHNICAL  NOTE.— 

Vinegar-eels  from  mouldy  vinegar,  and  hair-worms  from  fresh- 
water pools,  can  usually  be  readily  obtained.  They  should  be 
examined,  and  drawings  should  be  made  of  them,  showing  their 
shape  and  simple  external  structural  character.  If  a  specimen  of 
trichinosed  pork  be  obtained,  the  encysted  stage  of 
the  Trichina,  described  in  the  following  account,  can 
be  shown. 

The  roundworms  are  slender,  smooth, 
cylindrical  worms  pointed  at  both  ends. 
They  are  all  very  long  in  proportion  to  their 
diameter,  although  their  actual  length  may 
be  short.  Some  species  are  of  microscopic 
size;  as  the  Trichina  worm,  which  is  about 
^  in.  long;  while  the  guinea-worm,  one  of 
the  worst  parasites  of  man,  may  reach  a 
length  of  six  feet.  Many  of  the  round- 
worms  are  parasites  living  in  the  various 
organs  of  other  animals.  Some,  however, 
lead  an  independent  free  life  in  water  or  in 
damp  earth. 

Familiar  examples  of  roundworms  are  the 
so-called  vinegar-eels  (Anguilluld)  (fig.  32) 
to  be  found  in  weak  vinegar,  and  other 
species  of  this  same  genus  which  live  in  water 
or  moist  ground  or  in  the  tissues  of  plants, 
doing  much  injury.  The  hair-worms  (Gor- 
dius)  or  horse-hair  snakes,  which  are  believed 
by  some  people,  to  be  horse-hairs  dropped 
into  water  and  turned  into  these  animals,  are 
also  familiar  examples  of  roundworms.  They 
are  often  found  abundantly  in  little  pools  after  a  rain,  and 


FIG.  32.  —  A 
vinegar  eel, 
Anguiilula 
sp.  (From 
a  living 
specimen.) 


BRANCH   HERMES:    THE   WORMS 


141 


it  is  sometimes  said  that  these  worms  come  down  with  the 
rain.  They  have  in  reality  come  from  the  bodies  of  insects 
in  which  they  pass  their  young  or  larval  stages  as  parasites. 
The  hair-worms  all  live  as  parasites  during  their  larval 
stage,  and  as  free  independent  animals  in  their  adult  stage. 
Some  of  them  require  two  distinct  hosts  for  the  comple- 
tion of  their  larval  life,  living  for  a  while  in  the  body  of 

one,  and  later  in  the  body  of 
another.  The  first  host  is 
usually  a  kind  of  insect  which  is 
eaten  by  the  second  host.  The 
eggs  are  deposited  by  the  free 
adult  female  in  slender  strings 
twisted  around  the  stems  of 
water-plants.  The  young  hair- 
worm on  hatching  sinks  to  the 
bottom  of  the  pond,  where  it 
moves  about  hunting  for  a  host 
in  which  to  take  up  its  abode. 

The  terrible  TricJiina  spiralis 
(fig-  33)'  which  produces  the 
disease  called  trichinosis,  is 
another  roundworm  of  which 
much  is  heard.  This  is  a  very 
small  worm  which  in  its  adult 
condition  lives  in  the  intestine 
of  man  as  well  as  in  the  pig  and 
other  mammals.  The  young, 
which  are  borne  alive,  burrow 
through  the  walls  of  the  intes- 
tine, and  are  either  carried  by  the  blood,  or  force  their 
way,  all  over  the  body,  lodging  usually  in  muscles. 
Here  they  form  for  themselves  little  cells  or  cysts  in 
which  they  lie.  The  forming  of  these  thousands  of  tiny 
cysts  injures  the  muscles  and  causes  great  pain,  sometimes 


FIG.  33. —  Trichina  spiralis,  en- 
cysted in  muscle  of  a  pig. 
(From  specimen.) 


142  ELEMENTARY  ZOOLOGY 

death,  to  the  host.  Such  infested  muscle  or  flesh  is  said 
to  be  "trichinosed,"  and  the  flesh  of  a  trichinosed 
human  subject  has  been  estimated  to  contain  100,000,000 
encysted  worms.  To  complete  the  development  of  the 
encysted  and  sexless  Trie hince  the  infested  flesh  of  the 
host  must  be  eaten  by  another  animal  in  which  the  worm 
can  live,  e.g.  the  flesh  of  man  by  a  pig  or  rat,  and  that 
of  a  pig  by  man.  In  .such  a  case  the  cysts  are  dissolved 
by  the  digestive  juices,  the  worms  escape,  develop  repro- 
ductive organs  and  produce  young,  which  then  migrate 
into  the  muscles  and  induce  trichinosis  as  before.  But 
however  badly  trichinosed  a  piece  of  pork  may  be, 
thorough  cooking  of  it  will  kill  the  encysted  Trichina,  so 
that  it  may  then  be  eaten  with  impunity.  Some  people, 
however,  are  accustomed  to  eat  ham,  which  is  simply 
smoked  pork,  without  cooking  it,  and  in  such  cases  there 
is  always  great  danger  of  trichinosis. 

Wheel  animalcules  (Rotifera). — TECHNICAL  NOTE.-  Live 

specimens  of  Rotifers  can  be  found  in  almost  any  stagnant  water 
Examine  a  drop  of  such  water  with  the  compound  microscope,  and 
find  in  it  a  few  small,  active,  transparent  creatures,  larger  than  the 
Paramcccium  and  other  Protozoa  in  the  water  and  which  have  the 
appearance  shown  in  fig.  34.  They  may  be  known  by  the  constant 
whirling,  or  rather  vibrating,  circlet  or  wheel  of  cilia  at  the  larger 
or  head  end  of  the  body.  These  wheel  animalcules  may  be  studied 
alive  by  the  class.  Although  usually  darting  about,  the  animalcules 
occasionally  cease  to  move,  when,  because  of  their  transparency, 
almost  the  whole  of  their  anatomy  can  be  made  out.  Their  feeding 
habits  can  also  be  readily  observed,  and  the  food  itself  watched 
as  it  moves  through  the  body.  Make  drawings  showing  as  much 
of  the  anatomy  as  can  be  worked  out.  Note  especially  the  "mas- 
tax  "  or  gizzard-like  masticating  apparatus  in  the  alimentary  canal. 

The  wheel  animalcules  (fig.  34)  or  Rotifers  look  little 
like  the  other  worms  we  have  studied.  But  they  are 
nevertheless  more  nearly  related  to  the  worms  than  to 
any  other  branch  of  animals.  They  are  all  small,  about  £ 
mm.  long,  and  have  a  compact  body.  They  are  aquatic 
and  feed  on  smaller  animals  and  plants  or  on  bits  of  or- 


BRANCH   I/ERMES:    THE   WORMS 


ganic  matter  which  they  capture  by  means  of  the  currents 
produced  by  the  vibrating  cilia  of  the  "  wheel.  "  Small  as 

they  are  they  have  a  complex 
body-structure,  with  well-or- 
ganized systems  of  organs. 
For  a  long  time,  however, 
they  were  classed  by  natural- 
ists with  the  Protozoa  on  ac- 
count of  their  size.  They  are 
found  all  over  the  world, 
mostly  in  fresh  wrater;  a  few 
are  marine.  More  than  700 
species  of  them  are  known. 

An  interesting  thing  about 
the  Rotifers  is  their  remark- 
able power  to  withstand  dry- 
ing-up.  When  the  water  in 
a  pond  or  ditch  evaporates 
some  of  the  Rotifers  do  not 

FIG.    14.  —  A    wheel     animalcule.     ...  -11  i   T 

Rotifer  sp.    (From  living  sped-  die,  but  simply  dry  up  and  he 

men,  Stanford  University.)  jn     tlie     dust,     shrivelled     and 

apparently  lifeless,  yet  really  in  a  state  of  suspended 
animation.  On  being  put  into  water  they  will  gradually 
fill  out  to  their  full  size  and  shape,  and  finally  resume  all 
their  normal  activities.  In  this  dried-up  condition  Rotifers 
may  persist  for  a  long  time,  several  years  even,  although 
otherwise  their  natural  life  is  short,  being  probably  of  not 
over  two  weeks'  duration.  Certain  other  of  the  lower 
animals  have  this  same  power  of  withstanding  desiccation. 


CHAPTER   XX 

BRANCH  ARTHROPODA:  CRUSTACEANS,  CEN- 
TIPEDS,   INSECTS,    AND    SPIDERS 

I  THE  great  branch  Arthropoda  includes  a  host  of 
"T— familiar  animals.  It  contains  more  species  than  any  other 
branch  of  the  animal  kingdom.  To  it  belong  the  cray- 
fishes, shrimps,  crabs,  lobsters,  water-fleas,  and  other  ani- 
mals which  compose  the  class  Crustacea ;  the  centipeds 
and  thousand-legged  worms  which  compose  the  class 
Myriapoda ;  the  true  or  six-footed  insects  forming  the  class 
Insecta,  which  includes  nearly  two-thirds  of  all  the  known 
species  of  animals;  and  the  scorpions,  mites,  ticks,  and 
spiders  which  constitute  the  class  Arachnida.  There  is 
also  a  fifth  class  in  the  branch  Arthropoda  which  includes 
a  few  species  of  animals  unfamiliar  to  us  but  of  great 
interest  to  zoologists. 

All  these  varied  kinds  of  animals  have  a  body  on  the 

^  annulate  or  segmented  type-plan,  like -that  shown  by  most 
worms,  but  they  differ  from  the  worms  in  possessing 
jointed  appendages,  used  for  locomotion  or  food  taking. 
There  is  typically  or  racially  one  pair  of  these  jointed  or 
segmented  appendages  on  each  segment  of  the  body,  but 
in  all  of  the  Arthropoda  some  of  the  segments  have  lost 
their  appendages.  The  body  is  covered  by  a  firm  cuticle 
or  outer  body-wall  called  the  exoskeleton.  This  exo- 
skeleton  serves  not  only  to  enclose  and  protect  the  soft 
parts  of  the  body  but  also  for  the  attachment  of  the  body 

144 


BRANCH  ARTHROPODA:   CRUSTACEANS  145 

muscles.  It  may  be  flexible  as  in  the  sutures  between 
the  body-segments  in  most  insects,  or  hard  and  rigid  as 
in  the  sclerites  of  the  segments.  The  firmness  is  due 
primarily,  and  in  the  insects  usually  solely,  to  a  deposit  in 
the  cuticle  of  chitin,  a  substance  probably  secreted  by  the 
underlying  cells  of  the  true  skin,  or  it  maybe  due  chiefly, 
as  in  the  crabs,  to  a  calcareous  deposit.  In  such  cases  it 
becomes  a  veritable  armor.  The  internal  organs  of  the 
Arthropods  show  a  more  or  less  obvious  segmentation 
corresponding  with  the  segmentation  of  the  body- wall. 
The  alimentary  canal  runs  longitudinally  through  the 
center  of  the  body  from  mouth  to  anal  opening.  The 
nervous  system  consists  of  a  brain  lying  above  the 
oesophagus  and  a  double  nerve-chain  running  backward 
from  beneath  the  oesophagus,  along  the  median  line  of 
the  ventral  wall,  to  the  posterior  extremity  of  the  body. 
This  ventral  nerve-chain  consists  of  a  pair  of  longitudinal 
commissures  or  cords  and  a  series  of  pairs  of  ganglia, 
arranged  segmentally.  The  two  ganglia  of  each  pair  are 
fused  more  or  less  nearly  completely  to  form  a  single 
ganglion,  and  the  nerve-cords  are  partially  fused,  or  at 
least  lie  close  together.  In  addition  there  is  a  smaller 
sympathetic  system  composed  of  a  few  small  ganglia  and 
certain  nerves  running  from  them  to  the  viscera,  this  sys- 
tem being  connected  with  the  main  or  central  nervous 
system.  In  this  group  the  organs  of  special  sense  reach 
for  the  first  time  a  high  stage  of  development.  Com- 
pound eyes  are  peculiar  to  Arthropoda.  The  heart  lies 
above  the  alimentary  canal.  Respiration  is  carried  on  by 
gills  in  the  aquatic  forms,  and  by  a  remarkable  system  of 
air-tubes  or  tracheae  in  the  land  forms  (insects).  The 
sexes  are  usually  distinct,  and  reproduction  is  almost  uni- 
versally sexual.  Most  of  the  species  lay  eggs. 

The  Arthropods  are  animals  of  a  high  degree  of  organ- 
ization.     The  extremely  diverse  life-habits  of  the  various 


146  ELEMENTARY  ZOOLOGY 

kinds  among  them  have  led  to  much  modification  and  to 
great  specialization  of  structure.  The  course  of  develop- 
ment, too,  is  made  very  complicated  by  the  elaborate 
metamorphosis  undergone  by  many  of  the  members  of  the 
branch. 

We  shall  study  the  Arthropoda  by  getting  acquainted 
with  a  few  examples  of  each  class  and  thus  learning  the 
special  class  characteristics. 


CLASS   CRUSTACEA:    CRAYFISHES,   CRABS,    LOBSTERS, 

ETC. 

THE    CRAYFISH    (Cambarus  sp.) 

Structure. — The  structure  of  the  crayfish  has  been 
already  studied  (see  Chapter  IV  and  figs.  3  and  4). 

Life- history  and  habifs. — Crayfish  frequent  fresh-water 
lakes,  rivers,  and  springs  in  most  parts  of  the  United 
States.  Many  of  them  perish  whenever  the  small  prairie 
ponds  dry  up.  But  some  burrow  into  the  earth  when  the 
dry  season  comes.  There  may  be  noticed  in  meadows 
where  water  stands  for  certain  seasons  of  the  year  many 
scattered  holes  with  slight  elevations  of  mud  about  them. 
These  are  mostly  the  burrows  of  crayfish.  During  the 
dry  season  the  crayfish  digs  down  until  it  reaches  water, 
or  at  least  a  damp  place,  where  it  rests  until  wet  weather 
brings  it  to  the  surface  once  more.  One  of  these  burrows, 
followed  in  digging  a  mining  shaft,  extended  vertically 
down  to  a  distance  of  twenty-six  feet,  where  the  crayfish 
was  found  tucked  snugly  away. 

The  eggs  are  carried  by  the  female  on  her  abdominal 
appendages.  Previous  to  the  laying  of  the  eggs  the 
female  rubs  off  all  foreign  matter  from  the  appendages, 
thus  preparing  them  for  the  reception  of  the  eggs.  This 
cleaning  is  done  with  the  fifth  pair  of  legs.  When  the 


BRANCH  ARTHROPODS:   CRUSTACEANS  147 

eggs  arc  ready  to  be  laid,  which  is  during  the  last  of 
March  or  in  April  in  the  Central  States,  a  sticky  secretion 
passes  out  of  the  openings  at  the  base  of  the  walking  legs 
and  smears  the  pleopods  of  the  abdomen.  The  eggs  as 
they  pass  out  are  fertilized  and  caught  on  the  pleopods, 
where  they  remain  attached  in  clusters.  After  some 
weeks  the  young  crayfishes  issue  from  the  eggs.  In 
general  appearance  they  are  not  very  unlike  the  adults. 
They  grow  very  rapidly  at  this  stage.  As  the  animal  is 
enclosed  in  a  hard  shell,  growth  can  only  take  place 
during  the  period  just  following  the  molt,  for  the  crayfish 
casts  its  skin  periodically,  and  it  is  while  the  new  shell  is 
forming  that  the  animal  does  its  growing.  The  crayfish 
when  it  molts  casts  not  only  the  exoskeleton,  but  also  the 
lining  of  part  of  the  alimentary  canal.  After  the  females 
have  hatched  their  young  many  die  in  the  shallow  pools, 
in  which  places  the  dried-up  skeletons  are  noticeable 

during  the  summer  months. 

• 

OTHER    CRUSTACEANS. 

Most  of  the  crustaceans  live  in  water,  a  few  being  found 
-  in  damp  soil  or  in  other  moist  places.  Some  are  fresh- 
water animals  and  some  marine.  They  vary  in  size  from 
the  tiny  water-fleas,  a  millimeter  long,  to  crabs  two  feet 
across  the  shell  or  sixteen  feet  from  tip  to  tip  of  legs. 
They  present  great  differences  in  form  and  general  ap- 
pearance of  body,  being  adapted  for  various  conditions 
of  life.  Some  crustaceans  live  as  parasites  on  other 
animals,  in  some  cases  on  other  crustaceans.  Such 
parasitic  species  have  the  body  much  modified  and  are 
hardly  to  be  recognized  as  members  of  the  class. 

Body  form  and  structure.  —  In  structural  character  and 
body  organization  the  Crustaceans  show,  of  course,  the 
general  characteristics  already  attributed  to  the  Arthro- 

nnrta     thf»   brnnrh  tn  \vhtrh   fViPV  Hplnnrr          The  character- 


Ms  ELEMENTARY  /.OOLOGY 

istics  which  distinguish  them  from  other  Arthropods  are 
the  possession  of  gills  for  respiration  (some  insects  have 
gills,  but  of  a  very  different  kind  as  will  be  seen  later), 
and  the  bi-ramose  condition  of  the  body  appendages,  each 
appendage  (excepting  the  antennules)  consisting  of  a 
single  basal  segment  from  which  arise  two  branches  made 
up  of  one  or  more  segments.  Of  the  form  of  the  crus- 
tacean body  few  generalizations  can  be  made. 

'There  is  no  [other]  class  in  the  animal  kingdom 
which  presents  so  wide  a  range  of  organization  as  the 
Crustacea,  or  in  which  the  deviations  in  structure  from  the 
4  type  form  '  are  so  striking  and  so  interesting  from  their 
obvious  adaptation  to  the  mode  of  life. ' '  For  this  reason 
no  attempt  will  be  made  to  discuss  in  general  terms  the 
form  of  ther  crustacean  body,  but  brief  accounts  will  be 
given  of  a  few  of  the  more  familiar  kinds  of  Crustacea 
which  will  serve  to  illustrate  this  remarkable  diversity  of 
body  form. 

Similarly  impossible*  is  it  also  to  give  a  general  account 
f  the  development  of  the  crustaceans.  The  sexes  are 
distinct  in  most  Crustacea,  and  there  is  often  great  differ- 
ence in  form  between  the  male  and  female.  A  certain 
amount  of  metamorphosis  takes  place  in  the  development 
of  all  crustaceans;  that  is,  the  young  when  hatched  from 
the  egg  differs,  often  decidedly,  in  appearance  and  structure 
from  the  parentx  and  in  the  course  of  its  post-embryonic 
development  undergoes  more  or  less  striking  change 
or  metamorphosis.  This  metamorphosis  is  often  very 
marked. 

Water-fleas  (Cyclops). — TECHNICAL  NOTE.— The  water- 
fleas  are  common  in  the  water  of  ponds  or  of 'slow  streams;  they 
may  often  be  found  in  the  school  aquarium.  They  are,  though 
small  (about  i  mm.  long),  readily  seen  with  the  unaided  eye  ;  they 
are  white,  rather  elongate,  and  have  a  rapid  jerky  movement.  Ex- 
amine specimens  alive  in  water  in  a  watch  glass.  Note  the  "split 
pear  "  shape,  broadest  near  the  front,  tapering  posteriorly,  flat  be- 


BRANCH  ARTHROPODS:   CRUSTACEANS 


149 


neath,  convex  above;  note  the  forked  stylets  at  tip  of  abdomen  ;  also 
the  two  pairs  of  antennae,  the  single  median  eye,  the  mandibles,  two 
pairs  of  maxillae,  and  five  pairs  of  legs  (last  pair  very  small).  There 
are  no  gills.  Some  of  the  specimens,  females,  may  have  attached  to 
the  first  abdominal  segment  on  either  side  an  egg  sac.  Make 
drawings  showing  all  these  structural  details.  Watch  the  Cyclops 
capturing  and  feeding  on  Paramcecium  or  other  small  animals. 

The    water-fleas    (Cyclops)    (fig.    35)    are    among    the 
\smallest  of  the  Crustacea.     They  are  extremely  abundant, 


7 


FIG.  35. — A  water- flea,  Cyclops  sp.     Female  with  egg-masses. 
(From  living  specimen.; 

having  great  power  of  multiplication.  "An  old  Cyclops 
may  produce  forty  or  fifty  eggs  at  once,  and  may  give 
birth  to  eight  or  ten  broods  of  children  living  five  to  six 


i5°-  ELEMENTARY  ZOOLOGY 

months.  As  the  young  begin  to  reproduce  at  an  early 
age,  the  rate  of  multiplication  is  astonishing.  The 
descendants  of  one  Cyclops  may  number  in  one  year 
nearly  4,500,000,000,  or  more  than  three  times  the  total 
population  of  the  earth,  provided  that  all  the  young  reach 
maturity  and  produce  the  full  number  of  offspring. ' '  The 
Cyclops  feed  on  smaller  aquatic  animals  such  as  Protozoa, 
Rotifera,  etc.  .They  in  turn  serve  as  food  for  fishes;  and 
because  of  their  immense  numbers  and  occurrence  in  all 
except  the  swiftest  fresh  waters  ' '  they  form  the  main  food 
of  most  of  our  fresh-water  fishes  while  young. '!  Many 
aquatic  insect  larvae  feed  almost  exclusively  on  them. 

Related  to  the  Cyclops  are  a  host  of  other  kinds  of 
minute  Crustaceans.  Among  these  the  so-called  fish-lice 
are  specially  interesting  because  of  their  parasitic  habits 
and  greatly  modified  and  degenerate  structure.  There 
are  many  kinds  of  these  parasitic  crustaceans  infesting 
fishes,  whales,  molluscs,  and  worms.  "  As  on  land  almost 
every  species  of  bird  or  mammal  has  its  own  parasitic 
insects,  so  in  the  water  almost  every  species  of  fish  or 
larger  invertebrate  has  its  parasitic  crustaceans."  Some 
of  the  most  common  of  these  parasites  attach  themselves 
to  the  gills  of  fishes.  Here  they  cling,  sucking  the  blood 
or  animal  juices  from  the  host.  In  form  of  body  they  do 
not  at  all  resemble  other  Crustaceans,  but  are  strangely 
misshapen.  They  are  often  worm-like,  or  sac-like,  with- 
out legs  or  other  locomotory  appendages.  As  with  other 
parasites  (see  Chapter  XXX)  an  inactive  dependent  life 
results  in  the  atrophy  and  loss  by  degeneration  of  the 
body-parts  concerned  with  locomotion  and  orientation. 

Wood  lice  (Isopoda). — TECHNICAL  NOTE.  — Specimens  of 
wood  lice,  pill  bugs,  or  damp  bugs,  as  they  are  variously  called,  may  be 
readily  found  in  concealed  moist  places,  as  under  stones  or  boards  on 
damp  soil.  They  are  often  common  in  houses,  near  drains  or  in  dark, 
damp  places.  Examine  some  live  wood  lice,  and  some  dead  speci- 
mens (killed  by  chloroform  or  in  an  insect-killing  bottle). 


BRANCH  ARTHROPODA  :   CRUSTACEANS  151 

Note  the  division  of  the  body  into  the  head,  thorax,  and  abdomen  ; 
find  the  eyes,  the  antenna;  and  the  mouthparts  (mandibles  and  maxillae 
are  usually  pressed  closely  together).  All  the  locomotory  append- 
ages are  adapted  for  walking  or  running,  not  swimming.  Note  the 
number  of  pairs  of  legs  ;  the  structure  of  a  leg  ;  find  gills  and  gill- 
covers.  Some  females  may  be  found  with  eggs  on  the  under  side 
of  the  thorax  near  the  bases  of  the  legs,  the  eggs  being  covered  by 
thin  membranous  plates.  Make  drawings  snowing  the  general 
form  and  character  of  body  and  details  of  legs,  gills,  etc.  Compare 
with  the  crayfish  and  Cyclops. 

The  wood-lice  (fig.  36)  are  among  the  few  Crustacea 
which  have  a  wholly  terrestrial  life.  They  run  about 
quickly  and  feed  chiefly  on  decaying 
vegetable  matter.  They  are  night 
scavengers.  They  have  the  body 
oval  and  convex  above,  rather  pur- 
plish or  grayish  brown,  and  smooth. 
Although  they  do  not  live  in  the 
water  they  breathe  partly  at  least  by 
means  of  gills  (though  they  may 
breathe  partly  through  the  skin). 
It  is  therefore  necessary  for  them  to 
live  in  a  damp  atmosphere  so  that  the 
facoi  seci^Tnot  ^1  Sil1  membranes  may  be  kept  damp. 


specnot 

termined.    (From  sped-  if  not  kept    moist    they    could    not 

men.) 

serve  as  osmotic  membranes. 
Lobsters,  Shrimps  and  Crabs  (Decapoda).  —  TECHNICAL 

NOTE.  —  Teachers  living  near  the  sea-shore  can  get  specimens  of 
live  and  dead,  lobsters,  shrimps,  and  crabs  in  the  markets.  Schools 
in  the  interior  should  have  a  few  preserved  specimens  for  examina- 
tion. These  specimens  should  be  compared  with  the  crayfish  ; 
although  differences  in  shape  of  body  are  evident,  the  character 
and  arrangement  of  body  parts  will  be  found  to  be  very  similar. 

The  largest  and  most  familiar  Crustaceans,  as  the  cray- 
fishes, lobsters,  shrimps,  prawns  and  crabs,  all  belong 
to  the  order  Decapoda,  or  ten-legged  Crustacea.  The 
members  of  this  order  have,  including  the  large  claws, 
ten  walking  feet;  they  all  have  eyes  on  movable  stalks, 


152  ELEMENTARY  ZOOLOGY 

and  the  front  portion  of  the  body  is  covered  by  a  horny 
fold  of  the  body-wall  called  the  carapace. 

The  lobsters  are  large  ocean-inhabiting  crustaceans 
which  are  very  like  the  fresh-water  crayfish  in  all  struc- 
tural characters.  They  live  on  the  rocky  or  sandy  ocean- 
bottom  at  shallow  depths.  They  feed  largely  on  decaying 
[  animal  matter.  They  are  caught  in  great  numbers  in 
so-called  "  lobster  pots, "  a  kind  of  wooden  trap  baited 
with  refuse.  "The  number  thus  taken  upon  the  shores 
of  New  England  and  Canada  amounts  to  between  twenty 
and  thirty  million  annually.  "  Live  lobsters  are  brownish 
i or  greenish  with  bluish  mottling;  they  turn  red  when 
boiled.  A  single  female  will  lay  several  thousand  eggs. 
The  eggs  are  greenish  and  are  carried  about  by  the  mother 
until  the  young  hatch.  The  young  are  free-swimming 
larvae,  until  they  reach  a  length  of  half  an  inch. 
^j  The  shrimps  and  prawns  are  mostly  marine,  though* 
some  species  live  in  fresh  water.  They  are,  like  the 
lobsters,  used  for  food.  Some  of  the  species  are  gregari- 
ous in  habit,  occurring  in  great  "  schools  "  of  individuals. 
Like  the  lobsters  they  crawl  about  on  the  sea-bottom 
feeding  on  decaying  animal  matter.  Shrimps  are  very 
abundant  near  San  Francisco,  where  extensive  "shrimp 
fishing  "  is  done  by  the  Chinese. 

.JkThe  crabs  (fig.  37)  differ  from  the  lobsters  and  cray- 
fishes and  shrimps  in  having  the  body  short  and  broad, 
instead  of  elongate.  This  is  due  to  the  special  widening 
of  the  carapace  and  the  marked  shortening  of  the 
abdomen.  The  abdomen,  moreover,  is  permanently  bent 
underneath  the  body,  so  that  but  little  of  it  is  visible  from 
the  dorsal  aspect.  The  number  of  abdominal  legs  or 
appendages  is  reduced.  When  the  tide  is  out  the  rocks 
and  tide-pools  of  the  ocean  shore  are  alive  with  crabs. 
They  "scuttle  "  about  noisily  over  the  rocks,  withdraw- 
ing into  crevices  or  sinking  to  the  bottom  of  the  pools 


BRANCH  ARTHROPODA:   CRUSTACEANS  153 

when  disturbed.  They  move  as  readily  backward  or 
sidewise,  "crab-fashion,"  as  forward.  They  are  of 
various  colors  and  markings,  often  so  patterned  as  to 


FIG.  37. — Some  crabs  and  barnacles  of  the  Pacific  coast;  the  short  sessile 
acorn  barnacles  in  the  upper  left-hand  corner  belong  to  the  genus  Bal- 
anus;  the  stalked  barnacles  in  the  upper  right-hand  corner  are  of  the 
species  Pollidpes  polymenus;  the  largest  crab  (upper  left-hand)  is 
Brachynotus  nudus;  the  one  in  left-hand  lower  corner  is  a  young  rock- 
crab,  Cancer  prodiictus;  the  crab  in  the  sea-weed  at  the  right  is  a  kelp- 
crab,  Epialtus  prodnctus,  while  the  two  in  snail-shells  in  lower  corner 
are  hermit-crabs,  Pagnms  samuelis.  (From  living  specimens  in  a  tide- 
pool  on  the  Bay  of  Monterey.  California.) 

harmonize  very  perfectly  with  the  general ^cplor  and  ap- 
pearance of  the  rocks  and  sea-weeds  among  which  they 


154  ELEMENTARY  ZOOLOGY 

live.  The  spider-crabs  are  especially  strange-looking  crea- 
XTHtures  with  unusually  long  and  slender  legs  and  a  com- 
paratively small  body-trunk.  They  include  the  Macro- 
cJieira  of  Japan,  the  largest  of  the  crustaceans.  Specimens 
of  this  crab  are  known  measuring  twelve  to  sixteen  feet 
from  tip  to  tip  of  extended  legs ;  the  carapace  is  only  as 
many  inches  in  width  or  length.  The  soft-shelled  crab 
is  a  species  common  along  our  Atlantic  coast.  It  is 
"soft-shelled  "  only  at  the  time  of  molting,  and  has  to 
be  caught  in  the  few  days  intervening  between  the  shed- 
ding of  the  old  hard  shell  and  the  hardening  of  the  new 
body-wall.  The  little  oyster-crabs  (Pinnotheres]  which 
live  with  the  live  oyster  in  the  cavity  enclosed  by  the 
oyster  shell  are  well-known  and  interesting  crabs.  They 
are  not  parasites  preying  on  the  body  of  the  oyster,  but 
are  simply  messmates  feeding  on  particles  of  food  brought 
into  the  shell  by  the  currents  of  water  created  by  the 
oysters. 

^~  Among  the  most  interesting  crabs  are  the  hermit  crabs 
(fig.  37),  familiar  to  all  who  know  the  seashore.  There 
are  numerous  species  of  these  crabs,  all  of  which  have  the 
habit  of  carrying  about  with  them,  as  a  protective  covering 
into  which  to  withdraw,  the  spiral  shell  of  some  gastropod 
mollusc.  The  abdomen  of  the  crab  remains  always  in 
the  cavity  of  the  shell ;  the  head  and  thorax  and  legs 
project  from  the  opening  of  the  shell,  to  be  withdrawn 
into  it  when  the  animal  is  alarmed  or  at  rest.  The 
abdomen  being  always  in  the  shell  and  thus  protected 
loses  the  hard  body- wall,  and  is  soft,  often  curiously 
shaped  and  twisted  to  correspond  to  the  cavity  of  the 
shell.  It  has  on  it  no  legs  or  appendages  except  a  pair 
for  the  hindmost  segment  which  are  modified  into  hooks 
for  holding  fast  to  the  interior  of  the  shell.  As  the 
hermit  crab  grows  it  takes  up  its  abode  in  larger  and 
larger  shells,  sometimes  killing  and  removing  piece-meal 


BRANCH  ARJHROPODA:   CRUSTACEANS  '55 

the  original  inhabitant.  Some  hermit  crabs  always  have 
attached  to  the  shell  certain  kinds  of  sea-anemones.  It 
is  believed  that  both  crab  and  sea-anemone  derive  advan- 
tage from  this  arrangement.  The  sea-anemone,  which 
otherwise  cannot  move,  is  carried  from  place  to  place  by 
the  crab  and  so  may  get  a  larger  supply  of  food,  while 
the  crab  is  protected  from  its  enemies,  the  predaceous 
fishes,  by  the  stinging  threads  of  the  sea-anemone,  and 
also  perhaps  by  the  concealment  of  the  shell  its  presence 
affords.  This  living  together  by  two  kinds  of  animals  to 
their  mutual  advantage  is  called  commensalism.  ^r  sym- 
biosis  (see  Chapter  XXXj.  The  hermit  crabs  are  not  true 
crabs,  but  are  more  nearly  related  to  the  crayfishes  and 
shrimps  than  to  the  true  broad-bodied,  short-tailed  crabs. 

Barnacles. — TECHNICAL  NOTE. — Specimens  of  barnacles  may 
be  got  readily  from  the  tide  rocks  or  from  piles  in  a  harbor.  In- 
terior schools  should  have,  if  possible,  specimens  preserved  in 
alcohol  or  formalin  for  examination.  The  "  shells  "  of  acorn  (ses- 
sile) barnacles  may  often  be  found  on  oyster  shells  (get  at  restau- 
rants). 

/  Crustaceans  which  at  first  glance  are  hardly  recogniz- 
able as  such  are  the  stafked^or  sessile  barnacles  (fig.  37) 
which  live  fixed  in  great  numbers  on  the  rocks  between 
the  tide  lines,  or  on  the  piles  supporting  wharves,  or  on 
the  bottom  of  ships  or  even  on  the  body-wall  of  whales 
and  other  ocean  animals.  In  the  stalked  forms  the  stalk 
is  a  flexible  stem  or  peduncle  covered  with  a  blackish 
finely-wrinkled  skin  bearing  at  its  free  end  the  greatly 
modified  body  of  the  barnacle.  This  body  is  enclosed  in 
a  sort  of  bivalved  shell  or  carapace  formed  by  a  fold  of 
the  skin  and  stiffened  by  five  calcareous  plates.  Within 
this  curious  shell  is  the  compact,  rather  worm-like  body- 
mass,  showing  little  or  no  indication  of  segmentation. 
The  legs,  of  which  there  are  usually  six  pairs,  are  much 
modified,  being  long,  feathery,  and  divtcTecT  nearly  to  the 


156  ELEMENTARY  ZOOLOGY 

base.  These  feathery  feet  project  from  the  opened  shell 
when  the  animal  i^undisturbed,  and  waving  about  in  the 
water  catch  small  animals  which  serve  as  the  barnacle's 
food.  When  disturbed  the  barnacle  withdraws  its  feet 
and  closes  tightly  its  strong  protecting  shell.  The  acorn- 
barnacles  have  no  stalk,  but  look  like  a  low  bluntly- 
pointed  pyramid,  this  appearance  being  due  to  the 
converging  arrangement  of  six  calcareous  plates  in  its 
body-wall. 

The  barnacles  present  several  unusual  conditions  with 
regard  to  the  internal  organs.  They  have  no  heart  nor 
any  blood-vessels ;  most  of  the  species  are  hermaphroditic ; 
and  there  are  other  indications  of  a  degenerate  condition. 
This  degeneration  of  the  barnacles  is  due  to  their  fixed 
Hfe,  the  results  of  which  are  like  those  of  a  parasitic  life. 
The  young  barnacles  when  hatched  from  the  egg  are  free- 
swimming  larvae  as  with  the  other  Crustacea.  They 
finally  attach  themselves  and  undergo  the  changes,  some 
of  them  of  degenerative  nature,  which  produce  the  body- 
structure  of  the  adult.  It  was  long  a  belief  among  many 
people  that  the  barnacle  produced  the  barnacle  goose. 
Pictures  in  ancient  books  show  the  young  barnacle  geese 
issuing  from  the*  opened  shell  of  the  barnacle.  The  early 
naturalists  believed  barnacles,  on  account  of  the  shell,  to 
be  a  kind  of  shell-fish  or  mollusc,  but  when  their  develop- 
ment was  thoroughly  worked  out,  it  became  evident  that 
they  belong  to  the  Crustacea. 


CHAPTER   XXI 

BRANCH   ARTHROPODA   (continued};    CLASS  IN- 
SECTA:    THE    INSECTS 

THE   LOCUST    (Melanoplus  sp.) 

TECHNICAL  NOTE. — Locusts  or  grasshoppers  are  common  and 
familiar  insects  all  over  the  country.  The  genus  Melanoplus  in- 
cludes numerous  species,  one  or  more  of  which  are  to  be  found  in 
almost  any  locality.  The  common  red-legged  locust  (M.  femur- 
rubruni}  of  the  East,  the  Rocky  Mountain  migratory  locust  (M. 
spretits],  of  the  West,  the  large  differential  (M.  differentialis}  and 
two-striped  (M.  bivittatus}  locusts  of  the  Southwest,  are  especially 
common  species.  All  the  members  of  the  genus  have  their  hind 
wings  uncolored,  and  the  front  wings  marked  with  a  longitudinal 
series  of  small  dots  more  or  less  distinct,  or  with  a  longitudinal  line. 
There  is  a  small  blunt  spine  or  process  projecting  from  the  ventral 
aspect  of  the  prothorax.  If  a  species  of  Melanoplus  cannot  be 
found,  any  other  locust  may  be  used,  although  there  are  some  slight 
variations  in  the  external  structure  of  the  various  species.  Fresh 
specimens  killed  in  a  cyanide  bottle  (for  preparing  see  p.  463)  are 
preferable  in  the  study  of  the  external  structure,  but  specimens 
preserved  in  alcohol  will  do. 

External  structure  (fig.  38). — Note  that  the  body  of 
the  grass-hopper  is  composed  of  successive  rings  or  seg- 
ments grouped  into  thre^  regions,  the  head  (anterior), 
thorax  (median),  and  abdomen  (posterior).  In  which 
region  of  the  body  are  the  segments  most  readily  distin- 
guished ?  Of  how  maji}t-srgmeri£s  <-ioes  the  head  appear 
to  be  composed  ?  The  thorax  is  composed  of  three 
segments  of  which  the  most  anterior,  to  which  is  attached 
the  front  pair  of  legs,  differs  from  the  succeeding  two, 
being  freely  movable  and  bearing  a  large  hood-  or  saddle- 
shaped  piece  on  its  dorsal  aspect.  To  the  other  two 
thoracic  segments  the  second  and  third  pair  of  legs  are 

157 


158  ELEMENTARY  ZOOLOGY 

attached,  as  are  also  the  two  pairs  of  wings.      The  re- 
maining segments  of  the  body  compose  the  abdomen. 
Note  the  smooth,   rather  firm  and  horny  character  of 


antennae 
/\ 


auditory  organ 
ocellus  I 

head    compound  eye  \ 


•-ovipositor 


femur* 
tibia/ 

tar  sal  segments 

FIG.  38. — The  red-legged    locust.   Mclanoplus  femitr  rubnim,   to  show  ex- 
ternal structure. 

the  body.  This  is  due  to  the  fact  that  the  skin  is  every- 
where covered  with  a  cuticle  in  which  is  deposited  a 
horny  substance  called  chitin.  The  cuticle  is  not  uni- 
formly firm  over  the  body.  At  the  junction  of  the  body 
segments  in  the  abdomen,  in  the  neck  and  between  the 
segments  of  the  legs,  in  fact,  wherever  motion  is  desir- 
able, the  cuticle  is  flexible,  thus  making  bending  of  the 
body-wall  possible.  Elsewhere,  however,  it  is  hard  and 
stiff,  serving  not  only  as  a  protective  coat  or  armor  over 
the  body,  but  also  affording  firm  places  for  the  attachment 
of  muscles. 

Insects  (and  all  other  Arthropods)  have  no  *  internal 
skeleton,  but,  in  this  firm  cuticle,  an  exoskeleton, 

Although  the  head  is  apparently  a  single  segment,  it 

*  There  are  in  many  forms  a  few  internal  projections  from  the  exterior 
cuticle  which  act  as  internal  skeletal  pieces. 


BRANCH  ARTHROPODS;   CLASS  INSECTS:    THE  INSECTS   159 

is  really  composed  of  six  or  seven  body  segments  greatly 
modified  and  firmly  fused  together.  Note  that  it  bears 
a  pair  of  large  compound  eyes  and  three  much  smaller 
simple  eyes  or  ocelli. 

TECHNICAL  NOTE. — Strip  off  a  bit  of  the  outer  covering  of  a 
compound  eye,  mount  on  a  glass  slide  and  examine  under  the 
microscope. 

Note  that,  as  in  the  crayfish,  each  compound  eye  is 
composed  externally  of  many  small  hexagonal  facets,  the 
outer  covering,  the  cornea,  being  simply  the  cuticular  cover- 
ing of  the  body,  in  this  place  transparent  and  divided  into 
small  facets.  Besides  the  eyes,  the  head  bears  also  several 
movable  appendages,  namely  the  antennce,  and  the 
mouth-parts.  Note  the  number,  place  of  insertion,  and 
segmented  character  of  the  antennae.  These  antennae  are 
sense-organs  and  are  used  for  feeling,  smelling,  and,  in 
some  insects,  for  hearing.  Note  that  the  mouth-parts 
consist  of  an  upper,  broad,  flap-like  piece,  the  *labrum;  of 
a  pair  of  brown,  strongly  chitinized,  toothed  jaws  or 
mandibles;  of  a  second  pair  of  jaw-like  structures,  the 
maxillce,  each  of  which  is  composed  of  several  parts ;  and 
of  an  under,  freely-movable  flap,  the  labium,  also  com- 
posed of  several  pieces.  Each  maxilla  bears  a  slender 
feeler  or  palpus  composed  of  five  segments.  The  labium 
bears  a  pair  of  similar  palpi,  which  are,  however,  only 
three-segmented.  The  mandibles  and  maxillae,  which 
are  the  insect  jaws,  move  laterally,  riot  vertically  as  with 
most  animals. 

Make  drawings  of  the  lateral  aspect  of  the  head ;  of  a 
bit  of  the  cornea ;  of  the  dissected  out  mouth-parts. 

Of  the  three  segments  of  the  thoracic  region  of  the 
body,  the  most  anterior  one  is  called  the  prothorax.  It 
is  freely  movable  and  has  a  large  hood  or  saddle-shaped 

*  The  labrum  differs  from  the  other  mouth -parts  in  not  being  composed  of 
a  pair  of  body  appendages  ;  it  is  simply  a  fold  or  flap  of  the  skin  of  the  head. 


160  ELEMENTARY  ZOOLOGY 

piece,  the  pronotnm,  on  its  dorsal  aspect,  and  a  blunt- 
pointed  tubercle  on  the  ventral  aspect.  The  foremost 
pair  of  legs  is  attached  to  the  prothorax.  The  next 
segment  is  the  me  so  thorax,  which  is  immovaly  fused  to 
the  next  thoracic  segment.  What  appendages  does  it 
bear  ?  The  third  segment  is  the  metathorax,  which 
besides  being  fused  with  the  mesothorax  in  front,  is 
similarly  fused  with  the  foremost  abdominal  segment 
behind.  What  appendages  does  the  metathorax  bear  ? 

Examine  one  of  the  fore  legs  and  note  that  it  is  com- 
posed of  a  series  of  unequal  parts  or  segments.  The 
segment  nearest  the  body  is  sub-globular  and  is  called 
the  coxa;  the  second  segment  is  smaller  than  the  coxa 
and  is  called  the  trochanter;  the  third,  known  as  the 
femur,  is  the  largest  of  all ;  the  fourth,  tibia,  is  long  and 
slender;  and  the  next  three,  the  last  of  which  is  the 
terminal  one  and  bears  a  pair  of  claws  and  between  them 
a  little  pad,  the  pulvillus,  are  called  the  tarsal  segments. 
Most  insects  have  five  tarsal  segments.  Note  the  great 
size  of  the  hindmost  or  leaping  legs.  Determine  the  seg- 
ments of  the  middle  and  hindmost  legs.  Make  a  draw- 
ing of  a  fore  leg. 

Examine  the  wings.  In  what  ways  do  the  front  wings 
differ  from  the  hind  wings  ?  The  front  wings  are  known 
as  the  wing  covers  or  tegmina.  Note  how  the  hind  wings 
fold  up  like  a  fan,  and  are  covered  and  protected  by  the 
wing  covers.  Draw  the  wings. 

The  abdomen  is  composed  of  a  number  of  segments 
most  of  which  resemble  each  other.  The  first  segment 
(immediately  behind  the  metathorax)  has  its  dorsal  and 
ventral  parts  widely  separated  by  the  cavities  for  the  in- 
sertion of  the  hindmost  legs.  The  ventral  part  of  this 
segment  is  dovetailed  into  the  ventral  part  of  the  meta- 
thorax and  appears  to  be  part  of  it.  In  the  dorsal  part 
of  this  segment  there  is  on  each  side  a  spot  where  the 


BRANCH  ARTHROPOD A;   CLASS  IN  SECT  A :    THE   INSECTS   161 

cuticle  is  only  a  thin  membrane.  At  these  places  are 
the  auditory  organs  or  ears  of  the  locust.  The  thin 
membranes  are  the  tympana.  Only  the  various  kinds  of 
locusts  and  those  insects  closely  related  to  them  have  ears 
of  this  kind.  Most  other  insects  are  believed  to  have  the 
sense  of  hearing  situated  in  the  antennae. 

The  abdominal  segments  from  second  to  eighth  are  ring- 
like  in  form  and  are  without  appendages.  There  is  on 
the  side  of  each  of  these  segments  near  its  front  margin  a 
tiny  opening  or  pore  called  a  spiracle.  These  spiracles 
are  the  breathing  pores  of  the  locust,  which  does  not  take 
in  air  through  its  mouth  or  any  other  opening  in  the  head. 
There  is  a  spiracle  near  each  ear  in  the  first  abdominal 
segment,  and  one  on  each  side  of  the  mesothorax  near 
the  insertion  of  the  middle  legs. 

The  terminal  segments  of  the  abdomen  are  provided 
with  certain  processes  which  are  different  in  male  and 
female.  The  female  has  at  the  tip  of  its  abdomen  two 
pairs  of  strong,  curved  pointed  pieces  which  compose  the 
ovipositor,  or  egg-laying  organ.  The  opening  of  the 
oviduct  lies  between  the  pieces.  The  male  has  a  swollen 
rounded  abdominal  tip,  with  three  short  inconspicuous 
pieces  on  the  dorsal  surface. 

Make  a  drawing  of  the  lateral  aspect  of  the  abdomen 
of  a  female  locust;  also,  of  a  male. 

For  a  more  detailed  account  of  the  external  anatomy  of 
a  locust  see  Comstock  and  Kellogg's  "  Elements  of  In- 
sect Anatomy,"  chap.  II. 

The  external  structure  of  the  grasshopper  should  be 
carefully  compared  with  that  of  the  crayfish;  pay  special 
I  attention  to  the  mouth-parts  and  legs. 

The  teacher  should  point  out  the  homologies  and 
;  modifications. 

Life-history  and  habits.  — The  eggs  of  the  locust  are 
\  laid  in  the  autumn  in  the  ground  in  bare  dry  places, 


1 62  ELEMENTARY  ZOOLOGY 

as  roadsides,  closely-grazed  pastures,  etc.  The  female 
thrusts  her  strong  ovipositor  into  the  soil,  and  by  opening 
and  shutting  it,  thus  boring,  pushes  in  the  abdomen  for 
about  two  thirds  its  length.  The  eggs,  about  one  hun- 
dred, are  then  deposited  in  a  capsule  or  pod.  The  young 
locusts  hatch  in  the  following  spring.  When  just 
hatched  they  resemble  the  parent  locust  in  general 
appearance  and  structure  except  that  they  lack  wings, 
and  are  of  course  very  small.  The  young  locusts  are 
gregarious,  congregating  in  warm  and  sunny  places. 
They  feed  on  green  plants  and  travel  about  by  walking 
and  hopping.  At  night  they  try  to  find  shelter  under 
rubbish  in  the  fields.  They  feed  voraciously  and  grow 
rapidly,  reaching  maturity  in  about  two  months.  During 
this  post-embryonic  development  and  growth  they  molt 
(shed  the  chitinous  exoskeleton)  five  times.  After  the 
first  molt  indications  of  the  wings  appear  in  the  shape  of  \ 
small  backward  and  downward  prolongations  of  the  pos- 
terior margins  of  the  dorsum  of  the  mesothorax  and 
metathorax.  With  each  succeeding  molt  these  wing- 
pads,  or  developing  wings,  are  larger  and  more  wing-like, 
until  after  the  last  molting  they  appear  fully  developed. 
With  each  molting,  too,  there  is  a  marked  increase  in 
size  of  the  locust,  the  average  length  of  the  body  just 
before  the  first  moult  being  4.3  mm.,  before  the  second 
6.8  mm.,  before  the  third  9  mm.,  before  the  fourth  14 
mm.,  before  the  fifth  17  mm.,  and  after  the  fifth  (the  full- 
grown  stage)  about  26  mm. 

The  molting  is  an  interesting  process,  and  can  be 
readily  observed.  The  young  locust  ready  for  its  last 
molt  crawls  up  some  post,  weed,  grass  stalk,  or  other 
object,  and  clutches  this  object  securely  with  the  hind 
feet.  The  head  is  generally  downward.  The  locust 
remains  motionless  in  this  position  for  several  hours,  when 
the  skin  suddenly  splits  along  the  back  from  the  middle 


BRANCH  ARTHROPODA ;   CLASS  IN  SECT  A :    THE  INSECTS   163 

of  the  head  to  the  base  of  the  abdomen.  By  steady 
swelling  and  contracting  and  slight  wriggling,  lasting  for 
half  an  hour  to  three-fourths  of  an  hour,  the  old  skin  is 
completely  shed,  and  the  wings  spread  out.  In  an  hour 
the  wings  are  dry  and  the  new  chitinized  exoskeleton 
firm  enough  for  flying,  or  crawling  about,  and  in  another 
hour  the  locust  begins  to  eat. 

The  red-legged  locust  does  considerable  damage  to 
cultivated  crops,  but  its  injuries  are  insignificant  compared 
with  the  tremendous  losses  occasioned  by  a  near  relative, 
the  Rocky  Mountain  Locust  (Melanoplus  spretus}.  This 
locust  has  its  breeding-grounds  on  the  high  plateaus  of 
the  Rocky  Mountain  region,  but  it  sometimes  migrates  in 
countless  numbers  southeast  over  the  plains  and  into  the 
great  grain-fields  of  the  Mississippi  valley.  Such  migra- 
tions occurred  in  1866,  1867,  1874  (in  this  year  eighteen 
hundred  and  forty  two  families  in  Kansas  were  reduced 
to  destitution  by  the  utter  wiping  out  of  their  crops  by 
the  locusts)  and  1876.  With  the  settling-up  of  the 
regions  injvvhich  the  Rocky  Mountain  locust  breeds,  there 
seems  to  have  come  a  change  of  conditions,  so  that  no 
great  migrations  have  occurred  since  1876. 

THE   GREAT   WATER-SCAVENGER    BEETLE  (Hydrophilus  sp.) 

TECHNICAL  NOTE. — The  great  water-scavenger  beetles  are 
large,  black,  elliptical  insects  common  in  quiet  pools  where  they 
may  be  found  swimming  through  the  water,  or  crawling  among  the 
plants  growing  on  the  bottom.  They  are  an  inch  and  a  half  long 
and  are  readily  distinguishable  from  all  other  water  insects  except 
the  predaceous  diving  beetles  (Dytictts).  The  antennae  of  Hydro- 
philus, however,  are  thickened  (clavate)  at  the  tip,  while  those  of 
Dyticus  are  thread-like  for  their  whole  length.  The  beetles  may 
be  readily  collected  with  a  water-net,  and  kept  alive  in  glass  jars 
or  aquaria  in  water  containing  decaying  vegetation. 

External  structure  (fig.  39). — Is  the  body  of  the  water- 
beetle  composed  of  segments  ?  Can  you  make  out  three 
body-regions,  head,  thorax  and  abdomen  /  As  in  the 
locust  the  metathorax  is  fused  with  the  first  abdominal 


164 


ELEMENTARY  ZOOLOGY 


labial 

labium j 

compound  eye- 


mouth-parts 


palpi 
head 


coxa — 
trochanler- 


femur-' 
tibia 


tarsal  segments 


~prothorax 
-jnesothora 
metathorax 


abdom® 


FIG.  39.— Ventral  aspect  of  male  great  water-scavenger  beetle, 

ffydrophilus  sp« 


BRANCH  ARTHROPODS ;   CLASS  INSECTS:   THE  INSECTS  165 

segment  and  with  the  mesothorax,  while  the  prothorax 
is  freely  movable,  and  is  covered  above  by  a  strong  shield. 
The  chitin  armor  of  the  whole  body  is  specially  heavy 
and  strong,  affording  a  great  protection  to  the  insect. 

On  the  flattened  head  note  the  compound  eyes  and  the 
peculiarly-shaped  nine -segmented  antenna.  Are  there 
any  ocelli ?  Dissect  out  the  mouth-parts.  The  beetle's 
mouth  is  fitted  for  biting,  the  mouth-parts  being  in  general 
character  like  those  of  the  locust,  with  distinct  flap-like 
labnun,  dentate  mandibles,  jaw-like  maxillce  with  long, 
slender,  four-segmented  palpi  and  lip-like  labium  with 
three-segmented  palpi.  Make  drawings  of  the  antennae 
and  mouth-parts. 

Note  the  character  of  the  thoracic  segments.  Ex- 
amine the  wings  and  legs.  The  fore  wings  are  modified 
into  strong  horny  sheaths,  or  elytra,  which  completely 
cover  and  protect  the  folded  hind  wings.  The  hind  wings 
are  large  and  membranous.  How  are  they  folded  ?  Note 
the  adaptation  of  the  middle  and  hind  legs  for  swimming. 
Determine  the  various  segments  of  the  legs,  i.e.  coxa, 
trocJiantcr,  fcmnr,  tibia  and  tarsus.  Note  the  long  longi- 
tudinal median  keel  on  the  ventral  aspect  of  the  thorax. 

The  abdomen  articulates  with  the  metathorax  by  the 
full  width  of  the  broad  first  abdominal  segment.  It  is 
composed  of  a  series  of  segments  without  appendages,  of 
about  equal  length  but  decreasing  in  width  from  in  front 
backwards.  Of  how  many  segments  does  the  abdomen 
seem  to  be  composed  when  viewed  from  the  ventral 
aspect  ?  From  the  dorsal  ? 

Make  a  drawing  of  the  ventral  aspect  of  the  whole 
body. 

TECHNICAL  NOTE. — After  examining  the  abdomen  thus  far,  re- 
move it  from  the  rest  of  the  body,  and  boil  it  in  dilute  potassium 
hydrate  (KOH)  in  a  test-tube.  This  will  soften  and  partially  bleach 
the  body  wall, 


1 66  ELEMENTARY  ZOOLOGY 

Examine  the  softened  specimen,  and  note  that  at  least 
two  additional  segments  are  to  be  found  retracted  or  tele- 
scoped into  the  apparently  last  segment.  The  character 
of  these  terminal  abdominal  segments  differs  in  male  and 
female  individuals,  and  specimens  of  both  sexes  should  be 
examined.  (The  males  can  be  distinguished  from  the 
females  by  the  peculiar  pad-like  expansion  of  the  last 
tarsal  segment  of  the  fore  legs.)  Pull  out  the  retracted 
segments,  and  note  that  they  are  unevenly  chitinized, 
parts  of  their  surface  being  simply  membranous.  Project- 
ing backwards  are  several  long-pointed  processes.  The 
female  has  but  one  retracted-  segment.  Though  the 
females  of  many  insects  possess  more  or  less  elaborately 
developed  egg-laying  organs,  this  is  not  the  case  with  the 
beetles.  Look  for  spiracles  near  the  lateral  margins  of 
the  dorsal  surface  of  the  abdomen.  How  many  pairs  are 
present  ? 

Internal  Structure  (fig.4o). — TECHNICAL  NOTE. — If  fresh  speci- 
mens are  to  be  had,  kill  by  dropping  into  the  cyanide  bottle  (see  p. 
463).  Specimens  preserved  in  a  5$  solution  of  chloral  hydrate  may 
be  used  if  necessary.  When  putting  specimens  into  this  solution  a 
small  slit  should  be  cut  through  the  body  wall  to  allow  the  preserv- 
ative to  enter  the  body  cavity.  When  ready  to  dissect  a  specimen 
cut  off  the  elytra  and  wings  close  to  the  base,  and  carefully  remove 
all  of  the  dorsal  wall  of  the  abdomen  and  thorax  and  the  median 
portion  of  the  dorsal  wall  of  the  head.  Pin  ou%  ventral  side  down, 
under  water  in  a  dissecting-dish. 

Note  in  the  median  dorsal  line  of  the  abdomen  a  pale 
transparent  longitudinal  vessel,  the  heart  or  dorsal  vessel. 
Note  on  each  side  of  it  six  prominent  triangles  or  "  Vs  " 
with  apex  of  each  directed  laterally,  the  posteror  three 
smaller  than  the  anterior  three  of  each  side.  These  tri- 
angles are  formed  by  respiratory  tubes  or  trachea.  From 
each  spiracle  or  breathing-pore  there  extends  into  the 
body  a  respiratory  tube  or  trachea.  These  lateral  tracheae 
join  a  main  longitudinal  trachea  on  each  side,  from  which 


BRANCH   ARTHROPODA;   CLASS  INSECT  A :   THE  INSECTS  167 


are  given  off  branches,  which  in  turn  repeatedly  subdivide, 
until  all  parts  of  the  body  are  ramified  by  tracheae,  large 
and  small,  bringing  air  to  all  the  tissues.  The  oxygen  is 


brain 
oesophagus 


muscles 


.....crop 


elytron 


alimentary 

canal 

ventral  nerve 
chain 


wing 


.   , ,,         •%.  \          '^   N    .         —    Malpighian 
accessory  glands^'  fectum  ^L\ — ^Jr       *'  intestine        tubules 

\receptaculum~seminalis 

FIG.  40. —Dissection  of  female  great  water-scavenger  beetle,   Hydrophilus 
sp.,  the  heart  and  tracheae  being  cut  away. 

taken  up  from  this  air,  and  carbonic-acid  gas  is  given  up 
to  it,  when  it  passes  out  of  the  body  again  through  the 
spiracles.  Thus  in  the  insects  oxygen  and  carbonic-acid 


1 68  ELEMENTARY  ZOOLOGY 

gas  are  not  carried  by  the  blood  but  by  special  air-tubes. 
The  respiratory  system  of  insects  is  very  different  from 
that  of  other  animals. 

Mount  a  bit  of  trachea  in  glycerine  on  a  glass  slide  and 
examine  under  the  microscope.  Note  the  fine  spiral  line 
(looking  like  transverse  annular  striations)  which  is  a 
thickening  of  the  chitinous  inner  wall  of  the  tube  and 
which  by  its  elasticity  keeps  the  tracheal  tubes  open. 

The  heart,  already  noted,  is  composed  of  a  longitudinal 
series  of  very  thin-walled  chambers,  each  with  a  pair  of 
lateral  openings  into  the  body-cavity  and  with  terminal 
openings  into  the  adjacent  chambers.  The  blood,  which 
is  colorless  or  greenish  or  yellowish,  is  sent  forward 
through  the  successive  heart  chambers  by  regular  contrac- 
tions until  it  finally  pours  from  the  most  anterior  chamber 
freely  into  the  body-cavity.  Here  it  bathes  the  body- 
tissues,  flowing  perhaps  in  regular  paths,  giving  up  food 
to  the  tissues  and  taking  up  food  from  the  alimentary 
canal,  until  it  finds  its  way  through  the  lateral  openings 
into  the  heart  chamber  again.  There  are  no  arteries  or 
veins. 

Note  the  large  mass  of  muscles  in  the  metathorax. 
Note,  by  attempting  to  remove  it,  that  the  anterior  part 
of  the  muscle  mass  is  attached  to  a  chitinous  partition-wall 
between  the  meso-  and  meta -thorax.  Remove  this  parti- 
tion-wall (and  one  between  the  metathorax  and  abdomen) 
and  note  that  certain  muscles  run  deeply  down  into  the 
body.  By  pulling  on  the  bits  of  chitin  to  which  the 
muscles  are  attached,  the  muscles  (if  they  have  not  been 
cut)  can  be  stretched  to  the  length  of  three-quarters  of  an 
inch.  When  released  they  will  contract.  (This  stretch- 
ing and  contracting  takes  place  only  in  fresh  specimens.) 
What  are  these  large  and  numerous  muscles  of  the  thorax 
for? 

Remove  the  thin  membrane  stretching  over  the  abdomen 


BRANCH  ARTHROPODA ;   CLASS  INSECT  A:    THE  INSECTS    169 

and  in  which  the  heart  and  tracheal  "  Vs  "  lie,  and  note 
immediately  underneath  it  the  large  coiled  intestine  with 
a  knot  of  greenish  yellow  threads  in  the  centre.  Carefully 
uncoil  and  pin  out  the  intestine,  cutting  away  the  tying 
tracheae,  but  being  careful  not  to  cut  other  structures. 
Work  out  the  full  length  of  the  alimentary  canal,  noting 
the  oesophagus,  the  widened  crop  behind  it,  and  the  long 
intestine.  From  the  intestine  arise  several  greenish 
yellow  threads,  the  Malpigliian  tubules.  These  are  the 
excretory  organs  of  the  insect.  What  is  the  total  length 
of  the  alimentary  canal  ? 

The  reproductive  organs,  consisting  of  a  pair  of  glands 
(egg-glands  or  sperm-glands)  \vith  a  pair  of  tubes  which 
unite  before  reaching  the  body-wall  and  have  a  common 
external  opening,  may  now  be  seen.  These  should  be 
removed,  thus  exposing  the  ventral  nerve-chain  in  the 
abdomen.  To  expose  the  chain  in  the  thorax  it  will  be 
necessary  to  pick  away  carefully  the  muscles.  As  in  the 
crayfish,  the  central  nervous  system  in  the  beetle  consists 
of  a  ventral  nerve-chain,  a  brain  or  supra-ccsopJiageal 
ganglion  and  a  pair  of  circum-acsophagcal  commissures 
connecting  the  brain  and  the  foremost  ganglion  (infra- 
ccsophageal)  in  the  ventral  chain.  There  are,  in  the 
ventral  chain,  four  ganglia  in  the  thorax  and  four  in  the 
abdomen.  The  large  nerves  running  from  the  brain  to 
the  compound  eyes  and  to  the  antennae  can  be  traced. 

Make  a  drawing  showing  the  nervous  system. 

Life-history  and  habits.— The  eggs,  usually  about 
one  hundred,  are  deposited  in  a  silken  sac  or  case  which 
is  spun  by  the  female,  and  either  floats  freely  or  is  attached 
to  the  under  sides  of  the  leaves  of  aquatic  plants.  This 
egg-case  is  not  wholly  filled  with  eggs  but  has  a  consider- 
able air-chamber  in  it,  causing  it  to  float.  It  is  oval  in 
shape,  and  has  a  peculiar  curved  horn-like  projection  at 
the  upper  end.  In  sixteen  or  eighteen  days  the  young 


170  ELEMENTARY  ZOOLOGY 

water-scavenger  beetles  hatch  as  elongate,  wingless, 
active  larvae,  provided  with  three  pairs  of  legs  and  strong 
jaws.  They  remain  for  a  short  time  after  hatching  in  the 
egg-case,  feeding  on  each  other  !  After  they  issue  from 
the  case  they  feed  on  flies  or  other  insects  which  fall  into 
the  water,  and  on  snails.  They  breathe  through  a  pair 
of  spiracles  situated  at  the  posterior  tip  of  the  abdomen, 
coming  to  the  surface  and  thrusting  this  tip  up  so  that  the 
spiracles  are  out  of  water.  They  grow  rapidly,  molting 
three  times  before  becoming  full  grown.  They  attain  a 
length  of  nearly  three  inches.  -When  full  grown  they 
leave  the  water,  crawling  out  on  the  damp  shore  of  the 
pond  or  stream,  and  burrow  into  the  soil  for  a  few  inches. 
Here  they  molt  again,  or  pupate  as  it  is  called,  changing 
to  a  non-feeding,  quiescent  stage  called  the  pupal  stage. 
The  pupa  is  the  stage  in  which  the  great  changes  from 
wingless,  crawling  and  swimming,  short-legged,  long, 
slender-bodied  larva  to  winged,  swimming  and  flying, 
long-legged,  compact,  broad-bodied  adult  are  completed. 
Late  in  the  summer  or  in  the  fall  the  pupal  skin  breaks 
and  the  adult  issues.  It  works  its  way  to  the  surface  of 
the  ground,  and  betakes  itself  to  the  nearest  water. 

The  water-scavenger  beetle  shows  in  its  post-embryonal 
development  a  "  complete  metamorphosis  "  as  contrasted 
with  the  "incomplete  metamorphosis"  of  the  locust. 
Wherever  among  insects  similar  changes  occur,  the  young 
issuing  from  eggs  as  larvse  only  remotely  resembling  the 
parent,  and  these  active  feeding  larvae  changing  finally 
into  more  or  less  quiescent,  strictly  non-feeding  pupae, 
which  finally  change  into  the  active  adults,  a  complete 
metamorphosis  is  said  to  exist.  All  the  beetles,  the 
butterflies  and  moths,  the  two-winged  flies,  the  ants,  bees 
and  wasps,  and  certain  other  groups  of  insects  undergo  in 
their  post-embryonic  development  a  complete  metamor- 
phosis. The  crickets,  katydids,  the  sucking  bugs,  the 


BRANCH  ARTHROPODA;   CLASS  INSECT  A :    THE  INSECTS    ij1 

May-flics,  the  white  ants  and  numerous  other  insects 
have,  like  the  locust,  an  incomplete  metamorphosis,  that 
is,  the  young  when  hatched  resemble  in  most  respects, 
except  in  the  absence  of  wings,'  their  parents. 

The  adult  water-scavenger  beetle  feeds  chiefly  on 
decaying  vegetation  in  the  water,  but  instances  of  the 
taking  of  other  insects  and  of  snails  have  been  noted. 
Although  an  aquatic  insect  the  beetle,  like  its  larva,  has 
no  gills  for  breathing  the  air  which  is  mixed  with  the 
water,  but  has  to  come  to  the  surface  occasionally  to 
obtain  air.  This  it  does  in  an  interesting  way,  which 
should  be  carefully  observed  by  the  pupils.  The  air  is 
received  and  held  by  a  covering  of  fine  hairs  on  the  ven- 
tral surface  of  the  body,  so  that  a  considerable  supply  may 
be  carried  about  by  the*  beetle  while  underneath  the  sur- 
face. The  beetles  often  leave  the  water  by  night,  flying 
abroad  to  other  ponds  or  streams.  In  winter  the  beetles 
hibernate,  burying  themselves  in  the  banks  of  the  ponds 
which  they  inhabit. 

For  a  good  account,  with  illustrations,  of  the  water- 
scavenger  beetle's  life-history  see  Miall's  "  Natural  His- 
tory of  Aquatic  Insects,"  pp.  61-87. 

THE   MONARCH    BUTTERFLY    (Anosia  plexippns} 

TECHNICAL  NOTE. — The  Monarch  or  Milkweed  butterfly  is  dis- 
tributed ail  over  the  country.  It  is  large,  and  red-brown  in  color, 
and  lays  its  eggs  on  milk  weeds  where  the  greenish  yellow  and  black- 
banded  larvae  (caterpillars)  may  be  found  feeding.  The  covering 
of  scales  conceals  the  outlines  of  the  various  external  parts,  but 
these  scales  may  be  easily  removed  with  dissecting  needle  and  a 
small  brush.  In  brushing  the  scales  from  the  head  care  must  be 
taken  not  to  break  of  the  mouth-parts. 

External  structure  (fig.  41). — Note  the  three  body- 
regions,  Jicad,  tJiorax  and  abdomen.  Is  the  body  seg- 
mented ?  Note  the  dark  color  and  firm  character  of  the 
chitinized  cuticle. 


I72  ELEMENTARY  ZOOLOGY 

Note  on  the  head  the  large  compound  eyes.  Note  the 
tumid  convex  clypens  which  composes  most  of  the  anterior 
aspect  of  the  head.  Are  ocelli  present  ?  Compare  the 
antenna  with  those  of  the  locust  and  water-beetle.  Com- 
pare also  the  mouth-parts  and  note  that  they  differ  radi- 
cally from  those  of  the  locust  and  beetle.  They  are  not 
fitted  for  biting,  but  for  sucking  up  liquid  food  (the  nectar 
of  flowers).  Note  the  absence  of  a  movable  flap-like 
labrum  (a  minute  narrow  stiff  piece,  bearing  at  each  lateral 

compound  eye, 

antennae. /... 

prothorax\ 


labial 
palpi 

proboscis'' 


tarsal  segments 

FIG.  41. — Body  of  the  monarch  butterfly,  Anosia  plexippus,  with  scales  re- 
moved to  show  the  external  parts. 

end  a  small  group  of  fine  brown  hairs,  represents  the 
labrum),  the  entire  absence  of  mandibles,  and  the  absence 
of  a  movable  flap-like  labium.  The  labiiim  is  a  fixed 
chitinized  triangular  piece  forming  part  of  the  floor  of  the 
head.  Note  the  long  slender  proboscis  coiled  up  like  a 
watch-spring.  (In  fresh  specimens- this  proboscis  can  be 
uncoiled  and  will  be  found  flexible.  If  dried  or  alcoholic 
specimens  are  being  studied,  the  head  of  the  butterfly 


BRANCH  ARTHROPODS;   CLASS  INSECTA :    THE  INSECTS  i?3 

should  be  removed  and  softened  in  warm  water  before  the 
mouth-parts  are  examined.)  On  either  side  of  this 
proboscis  is  a  peculiar  pointed  process  which  rises  from 
the  under  side  of  the  head.  These  processes  are  the 
labial  palpi  and  serve  to  protect  the  sucking  proboscis. 
The  proboscis  itself  is  composed  of  the  two  greatly  modi- 
fied maxillce.  Instead  of  being  short,  jaw-like  and  com- 
posed of  several  pieces  as  in  the  locust,  in  the  butterfly 
each  maxilla  is  a  slender,  flexible  half  tube  applied  against 
its  mate  on  the  opposite  side  in  such  a  way  as  to  form  a 
perfect  tube  long  enough  to  reach  into  the  nectaries  of 
flowers  when  in  use  and  capable  of  being  compactly  coiled 
up  at  other  times.  Cut  across  the  proboscis  and  note  the 
canal  in  the  centre.  Try  to  separate  the  two  maxillae 
which  compose  it. 

Make  a  drawing  of  the  frontal  aspect  of  the  head  with 
the  eyes  and  appendages. 

Compare  the  thorax  with  that  of  the  beetle  and  that  of 
the  locust.  The  prothorax  is  a  freely  movable  narrow 
ring  or  collar.  The  mesothorax  and  metathorax  are  fused 
to  form  a  large  convex  mass,  of  which  fully  five-sixths  is 
mesothorax  and  only  one-sixth  metathorax.  Try  to  dis- 
tinguish the  boundaries  of  the  two  segments.  Note  the 
three  pairs  of  legs;  the  differences  in  size  among  them, 
and  the  differences  between  them  and  the  legs  of  the 
locust  and  water-beetle.  In  one  of  the  legs  determine 
the  coxa,  trochantcr,  femur,  tibia  and  tar  sal  segments. 
Note  the  differences  between  the  wings  of  the  butterfly 
and  those  of  the  locust  and  beetle.  Note  that  the  wings 
are  membranous,  but  are  covered  with  many  fine  scales 
(fig.  42),  as  is,  indeed,  the  whole  body.  Rub  off  some  of 
these  scales  on  a  glass  slide  and  examine ;  note  shape, 
little  stem  or  pedicel  of  insertion,  and  longitudinal  stria- 
tions.  Examine  under  microscope  a  bit  of  wing  from  which 
some  of  the  scales  have  been  rubbed.  How  are  the  scales 


i74 


ELEMENTARY  ZOOLOGY 


attached  to  the  wing1  membranes  ?  How  are  the  scales 
arranged  ?  Note  that  the  wing  is  colorless  where  the 
scales  have  been  removed.  All  the  colors  and  patterns 
of  the  wings  of  butterflies  are  produced  by  the  scales. 

Make  drawings  of  scales;  of  parts  of  denuded  wings, 
and  of  bit  of  wing  covered  with  scales. 

Remove  all  or  nearly  all  the  scales  from  a  wing  and 
note  the  arrangement  of  the  veins  (venation).  Compare 
with  venation  in  wings  of  locust. 

Make  drawing  showing  venation  in  the  butterfly's 
wings. 

The  venation  of  insects'  wings  is  much  used  in  insect 

classification,  and  the 
various  veins  have  been 
given  names.  The 
names  of  the  veins  in 
the  butterfly's  wings  are 
given  in  fig.  43.  When 
the  veins  in  the  wings 
of  all  the  various  groups 
of  insects  are  studied,  it 
is  evident  that  the  prin- 
cipal ones  are  the  same 
in  all  insects,  so  that 

FIG.  42-Bit  of  wing  of  monarch  butterfly,  the  COSta,  Sllb-CUSta,  ra- 
Anosia plexippus,  magnified  to  show  the  dius,  media,  Cubitus  and 


scales;  some  scales  removed  to  show  the 


anal  veins  of  the  butter- 


insertion-pits  and  their  regular  arrange- 
ment. (From  specimen.)  fly's  wings  can  be  com- 
pared with  the  corresponding  veins  in  the  wings  of  a 
beetle  or  wasp  or  fly.  Noting  the  differences  in  the  num- 
ber and  character  of  branching  of  these  principal  veins, 
and  the  number  and  disposition  of  the  cross-veins  which 
connect  the  longitudinal  veins,  the  various  kinds  of  insects 
can  be  to  a  large  extent  properly  grouped  or  classified. 
A  detailed  account  of  the  wing-veins  of  insects  is  given 


BRANCH  ARTHROPODA;   CLASS  IN  SECT  A  :    THE  INSECTS    i?5 

in  Comstock  and  Kellogg's    "  Elements  of  Insect  Anat- 
omy," chap.  VII. 

Of  how  many  segments  is  the  abdomen  composed  ? 
The  first  or  basal  segment  is  depressed,  while  the  others  are 
more  or  less  compressed.  The  spiracles  are,  as  in  the  locust, 
situated  on  the  lateral  aspects  of  the  abdominal  segments. 
What  segments  bear  spir- 
acles ?  The  terminal  seg- 
ments of  the  abdomen 
differ  in  the  two  species. 
In  the  female  the  dorsal 
part  of  the  Apparently) 
last  segment  is  longer 
than  the  ventral  part  and 
is  bent  down  over  it  form- 
ing  a  sort  of  hood  over  a 
space  enclosed  partly  by 
this  hood,  partly  by  a 
bluntly-pointed  projection 
from  the  ventral  surface, 
and  party  by  the  lateral 
margins  of  the  segment. 
In  this  chamber  lies  the 

Opening     from     which    the    FIG.  43.—  Wings  of  monarch  butterfly, 
eggs    issue.       In    the    male        Anosiaplexippas  to  show  venation  ;/ 

costal  vein  ;  sc,  sub-costal  vein;  r,  radial 

there      are      several     back-        vein;  r«,  cubital  vein;  a,  anal  veins. 
.-  i  In  addition  most  insects  have  a   vein 

ward  -  projecting,     horny,  ^^  the  sub  costal  and  ra_ 


thin  processes.  dial  veins  called  the  median  vein. 

Make  a  drawing  of  the  lateral  aspect  of  the  whole  body. 

Life-history  and  habits.  —  The  tiny,  conical,  yellowish- 
green  eggs  of  the  monarch  butterfly  are  deposited  on  the 
under  side  of  the  leaves  of  milkweeds  (Ascleptas}  and 
when  examined  under  the  microscope  are  seen  to  be  very 
beautiful  little  objects  finely  ribbed  with  longitudinal  and 
transverse  striae.  The  eggs  are  laid  in  April  and  May 
(depending  on  the  lacitude  and  season)  by  females  which 


176  ELEMENTARY  ZOOLOGY 

have  hibernated  in  the  adult  condition.  From  the  eggs 
the  minute,  cylindrical,  pale-green,  black-headed  larvae 
hatch  in  four  or  five  days.  As  soon  as  hatched  the 
larva  devours  the  eggshell  from  which  it  has  escaped  and 
then  feeds  voraciously  on  the  milkweed  leaves.  It  grows 
'rapidly,  and  in  three  or  four  days  a  blackish  band  or  ring 
appears  on  each  segment,  and  for  the  rest  of  its  life  it  is 
very  conspicuously  colored  with  its  black  rings  on  a 
yellowish-green  background.  It  molts  three  times,  and 
in  from  twelve  to  twenty  days  is  ready  to  pupate,  or 
change  to  a  chrysalis. 

When  ready  to  pupate  the  larva  usually  leaves  the 
milkweed  plant,  and  seeks  some  such  protected  place  as 
the  under  side  of  a  fence-rail  or  jutting  rock.  Here  it 
attaches  its  posterior  extremity  by  a  small  silken  web  to 
the  rail  or  rock,  and  casting  its  larval  skin  appears  as  a 
beautiful  pale-green  chrysalis  with  ivory  black  and  golden 
spots.  It  hangs  motionless,  and  of  course  without  taking 
food,  for  from  a  week  to  two  weeks  (according  to 
season  and  temperature),  when  the  pupal  cuticle  breaks 
and  the  great  red-brown  butterfly  (fig.  165)  issues. 

The  butterfly  feeds  fas  is  indicated  by  the  structure  of 
its  mouth-parts)  very  differently  from  the  larva;  it  sucks 
up  by  means  of  its  long  tubular  proboscis  the  nectar  of 
flowers,  nor  does  it  confine  itself  at  all  to  the  flowers  of 
milkweeds.  It  is  a  fine  flyer  and  a  great  traveller.  Many 
thousands  of  these  butterflies  often  make  long  flights  or 
migrations  together.  At  other  times  tens  of  thousands 
of  these  butterflies  congregate  in  a  certain  limited  area, 
clinging  sometimes  to  the  branches  of  a  few  trees  in  such 
numbers  and  so  closely  together  as  to  give  the  tree  a 
brown  color.  Such  a  "  sembling  "  of  monarch  butterflies 
occurs  every  year  near  the  Point  Pinos  lighthouse  on 
the  Bay  of  Monterey,  California.  The  object  of  this 
assembling  together  is  not  understood.  Both  the  larvae 
and  adults  of  the  monarch  butterfly  are  distasteful  to  birds, 


BRANCH  ARTHROPODA;   CLASS  IN  SECT  A  :    CHE  INSECTS  *77 

by  their  possession  of  an  acrid  body-fluid.  The  species 
is  thus  protected  against  the  most  dangerous  enemies  of 
butterflies,  a  fact  which  chiefly  accounts  for  the  great 
abundance  and  wide  distribution  of  the  monarch  (see 
p.  137).  For  a  full  account  of  the  life-history  of  the 
monarch  butterfly,  see  "Scudder's  Life  of  a  Butterfly." 

LARVA   OF   MONARCH    BUTTERFLY  (Anosia  plexippus) 

TECHNICAL  NOTE. — For  directions  for  finding  and  identifying  the 
larvae  of  the  monarch  butterfly  see  p.  171.  If  larvae  (caterpillars)  of 
Anosia  cannot  be  found,  those  of  any  other  butterfly  or  moth  will 
do.  Use  naked,  smooth  kinds  like  cutworms,  cabbage  worms  and 
the  like,  rather  than  hairy  or  spiny  ones.  Use  large  specimens. 
Kill  the  caterpillar  with  ether  or  in  a  cyanide  bottle. 

Structure  (fig.  44). — As  we  have  learned  from  the  study 
of  the  life-history  of  the  locust,  water-beetle  and  butterfly, 
some  insects  are  hatched  from  the  egg  in  a  condition 
resembling  that  of  the  parents  in  most  structural  charac- 
ters. This  is  true  of  the  locust.  Other  insects,  as  the 
beetle  and  butterfly,  are  hatched  in  a  form  and  condition 
apparently  very  different  from  that  of  the  parents.  The 
external  appearance  of  a  beetle  or  butterfly  larva  differs 
much  from  that  of  the  adult  or  imago  of  the  same  indi- 
vidual. It  will  be  of  interest  to  examine  more  particu- 
larly the  structural  condition  of  one  of  these  larvae  and  to 
compare  it  with  the  structure  of  the  adult. 

Is  the  body  segmented  ?  Is  the  body  composed  of 
head,  thorax  and  abdomen?  Note  the  soft,  flexible, 
weakly-chitinized  condition  of  the  body-wall.  How  many 
pairs  of  legs  are  there  ?  Where  are  they  situated  ?  Is 
there  any  difference  in  the  various  legs  ?  If  so,  what  is 
the  difference  ?  Which  of  the  legs  of  the  larva  correspond 
with  the  legs  of  the  butterfly  ?  Why  ?  The  prothoracic 
segment  and  the  abdominal  segments  I  to  8  each  bear  a 
pair  of  spiracles  (small  blackish  spots  on  the  sides).  Are 
both  compound  and  simple  eyes  present  ?  How  many  eyes 


I78 


ELEMENTARY  ZOOLOGY 


Q3 


BRANCH  ARTHROPODA ;   CLASS  INSECT  A :    THE  INSECTS  179 

are  there  ?  Are  there  antenna  ?  Dissect  out  the  month- 
parts.  How  do  they  differ  from  those  of  the  butterfly  ? 
Are  they  more  like  the  mouth-parts  of  the  butterfly  or 
more  like  those  of  the  locust  ? 

With  fine  sharp-pointed  scissors  make  a  shallow  longi- 
tudinal incision  along  the  whole  length  of  the  dorsal  wall. 
In  a  freshly-killed  specimen  a  drop  of  pale  greenish  blood 
will  issue  as  the  scissors'  point  is  first  thrust  through  the 
skin.  Put  a  droplet  of  this  blood  on  a  glass  slide,  cover 
with  cover  glass  and  examine  with  high  power  of  the 
microscope.  Note  that  the  blood  is  a  fluid  containing 
numerous  sub-circular  or  elliptical  bodies,  the  blood- 
corpuscles.  Note  at  least  two  kinds  of  corpuscles :  most 
abundant  a  granular,  circular  kind,  the  true  blood-corpus- 
cles ;  and  rarer,  a  larger,  clear,  usually  elliptical  or  oval, 
but  sometimes  irregular  and  amoebiform  kind,  generally 
spoken  of  &§  fat -cells. 

Make  a  drawing  of  the  corpuscles  in  the  field  of  the 
microscope. 

After  making  the  dorsal  longitudinal  incision  pin  out 
the  caterpillar  in  the  dissecting-dish  with  dorsal  aspect 
uppermost.  When  the  edges  of  the  skin  are  pinned  back, 
the  organs  most  conspicuous  in  the  body-cavity  will  be 
the  flocculent  masses  of  adipose  tissue,  the  large,  simple, 
tubular  alimentary  canal  usually  dark  or  greenish  because 
of  the  color  of  its  contents,  and  the  numerous  silvery 
tracJieal  tubes.  In  those  caterpillars  which  spin  a  silken 
cocoon,  the  silk  or  spinning-glands  are  usually  long  and 
prominent.  They  lie  on  either  side  of  the  anterior  part 
of  the  alimentary  canal,  and  open  by  a  common  duct  on 
the  labium.  Rising  from  behind  the  middle  of  the  ali- 
mentary canal  maybe  found  the  long,  whitish,  folded  and 
twisted  MalpigJiian  tubules.  By  picking  away  the  fat 
masses,  expose  the  full  length  of  the  alimentary  canal. 
Note  its  great  size  (large  diameter).  Is  it  divided  into 


i8o  ELEMENTARY  ZOOLOGY 

distinct  regions  such  as  crop,  proventriculus,  stomach, 
intestine,  etc.  ?  How  is  it  held  in  place  ?  Trace  the 
principal  longitudinal  trachea!  trunks.  Find,  if  you  can, 
a  pair  of  small  compact  bodies  usually  somewhat  elongate, 
one  lying  on  each  side  of  the  posterior  part  of  the  alimen- 
tary canal.  These  are  the  rudimentary  reproductive 
organs. 

Remove  the  alimentary  canal  by  cutting  it  off  at  its 
posterior  tip  and  also  in  the  prothoracic  segment.  Work 
out  now  the  ventral  nerve-cord  and  ganglia,  and  the 
supra-asophageal  (brain)  and  infra-oesophageal  ganglia 
and  the  commissures  in  the  head. 

In  the  body  of  the  caterpillar  we  have  found  the  same 
general  disposition  of  organs  as  in  the  body  of  an  adult 
insect,  but  several  differences  are  nevertheless  noticeable, 
viz.,  the  presence  of  a  large  quantity  of  fatty  tissue,  the 
great  size  and  simple  character  of  the  alimentary  canal, 
and  the  undeveloped  condition  of  the  reproductive  organs. 


OTHER    INSECTS 

The  class  Insecta  includes  those  Arthropods  which 
have  one  pair  of  antennae  (sense  appendages),  three  pairs 
of  mouth-parts  (oral  appendages),  and  three  pairs  of  legs 
(locomotory  appendages).  The  insects,  in  further  con- 
tradistinction to  the  crustaceans,  are  mostly  land  animals 
and  breathe  by  means  of  tracheae  or  tracheal  gills.  They 
are  the  most  familiar  of  land  invertebrates,  and,  as  already 
mentioned,  include  more  species  than  are  comprised  in  all 
the  other  groups  of  animals  taken  together.  Beetles, 
moths  and  butterflies,  flies,  wasps  and  bees,  dragonflies 
and  grasshoppers  are  familiar  members  of  the  class  of 
insects,  but  spiders,  mites,  scorpions,  centipeds  and 
thousand-legged  worms  are  not  true  insects  and  should 


BRANCH  ARTHROPOD/1;  CLASS  1NSECTA :   THE  INSECTS  181 


not  be  so  miscalled.  These  last  belong  to  the  branch 
Arthropoda  but  to  other  classes  than  the  class  Insecta. 
While  insects  are  found  living  under  most  diverse  condi- 
tions on  land,  that  is,  on  the  ground,  in  the  leaves,  fruits 
and  stems  of  plants,  in  the  trunks  of  trees  or  in  dead 
wood,  in  the  soil,  in  decaying  animal  or  plant  matter,  as 
parasites  on  or  in  other  animals,  and  in  all  fresh-water 
ponds  and  streams,  they  do  not  live  in  ocean  water.  A 
few  species  live  habitually  on  the  surface  of  the  ocean,  and 
a  few  other  forms  are  found  habitually  on  the  water- 
drenched  rocks  and  seaweeds  between  tide  lines.  The 
varied  habits  of  insects,  their  economic  relations  with 
man.  the  beauty  and  grace  of  many  of  them,  and  the 
readiness  with  which  they  may  be  collected,  reared  and 
studied,  renders  them  unusually  fit  animals  for  the  special 
attention  of  beginning  students  of  zoology. 

Body  form  and  structure.  — The  segments  composing 
the  body  of  an  insect 
are  grouped  to  form 
three  body-regions,  the 
head,  thorax,  and  abdo- 
men. The  head  of  an 
adult  insect  appears  to 
be  a  single  segment  or 
body-ring,  but  in  reality 
it  is  composed  of  several 
segments,  probably 
seven,  completely  fused. 
The  head  bears  the  eyes, 
antennae  and  the  mouth- 
parts.  The  thorax  is 
made  up  of  three  seg- 
ments, each  segment 
bearing  a  pair  of  legs. 
From  the  dorsal  side  of  the  hinder  two  thoracic  segments 


FIG.  45. — A  wingless  insect;  the  American 
spring-tail.  Lepidocyrtus  americanus, 
common  in  dwelling-houses.  The  short 
line  at  the  right  indicates  the  natural 
size.  (From  Marlatt.) 


182  ELEMENTARY  ZOOLOGY 

arise  the  two  pairs  of  wings  which  are  the  most  striking 
structural  features  of  insects.  Not  all  insects  are  winged, 
(fig.  45),  and  of  those  which  are  a  few  have  only  one  pair 
of  wings,  but  the  great  majority  of  them  have  two  pairs  of 
well-developed  wings  (fig.  46),  which  give  them,  as  com- 
pared with  the  other  animals  we  have  studied,  a  new  and 
most  effective  means  of  locomotion.  The  great  numbers 


FIG.   46. — A   four- winged  insect;     a    stone  fly,   Per  la    sp.,    common    about 
brooks.     (From  Jenkins  and  Kellogg.) 

of  insects  and  their  preponderance  among  living  animals 
is  undoubtedly  largely  due  to  the  advantage  derived  from 
their  power  of  flight.  The  hindmost  part  of  the  body, 
the  abdomen,  is  composed  of  from  seven  to  eleven  seg- 
ments, only  the  last  one  or  two  of  which  are  ever  provided 
with  appendages.  When  such  posterior  abdominal 
appendages  are  present  they  form  egg-laying  or  stinging 
or  clasping  organs. 


BRANCH  ARTHROPODA;   CLASS  INSECT  A :   THE  INSECTS   1^3 

The  body-wall  is  usually  firm  and  rigid,  with  thinner 
flexible  places  between  the  segments  and  body-parts  for 
the  sake  of  motion.  The  body-wall  is  composed  of  a 
cellular  skin  or  hypoderm,  and  an  outer  non-cellular 
cuticle  in  which  is  deposited  a  horny  substance  called 
chitin.  This  chitinous  cuticle  or  exoskeleton  serves  as 
an  armor  or  protective  covering  for  the  soft  body  within, 
and  also  as  a  point  of  attachment  for  the  many  muscles 
of  the  body. 

Insects  vary  a  great  deal  in  regard  to  shape  and  ap- 
pearance of  the  body,  and  certain  of  the  external  organs 
are  greatly  modified  in  different  insects  to  adapt  them  to 
the  varied  conditions  under  which  they  live.  Especially 
interesting  and  important  are  the  variations  in  the  char- 
acter of  the  mouth-parts  and  wings,  the  organs  of  food- 
getting  and  locomotion.  In  our  consideration  later  of 
some  of  the  more  important  groups  of  insects  the  modifica- 
tion of  these  parts  will  be  specially  referred  to.  Despite 
the  great  number  ol  insects,  however,  and  their  varied 
habits  of  life,  a  strong  uniformity  of  body-structure  is 
noticeable,  all  of  them  holding  pretty  closely  to  the 
typical  body-plan. 

The  most  interesting  feature  of  the  internal  anatomy  of 
the  insect  body  is  the  respiratory  system.  Insects  breathe 
through  tiny  paiied  openings,  called  spiracles,  in  the  sides 
of  the  abdominal  (and  sometimes  the  thoracic)  segments 
(the  number  and  disposition  of  the  pairs  of  spiracles  varying 
much  in  different  insects).  These  spiracles  are  the  external 
openings  of  an  elaborate  system  of  air-tubes  or  tracheae 
(fig.  47)  which  ramify  throughout  the  whole  body  and  carry 
air  to  all  the  organs  and  tissues.  The  blood  has  apparently 

(nothing  to  do  with  respiration  as  it  has  in  the' vertebrate 
animals,  where  it  carries  oxygen  to  all  the  body  tissues. 

The  other  systems  of  organs  are  well  developed  and  in 
many  respects  more  complex  and  elaborate  than  those  of 


ELEMENTARY  ZOOLOGY 


any 


of  the 


The  alimen- 


FIG,   47. — Piece 


other  invertebrates.       The  muscular  system 
comprises  a  large  number  of  distinct  mus- 
cles,  usually  small  and  short,  which    are 
disposed  so  as  to   make  very  effective  the 
various     complex    motions     of    antennae, 
mouth-parts,  legs,  wings,  and  egg-laying 
organs.      The  muscles  appear  to  be 
very  delicate,  being  almost  colorless 
when  fresh,  but  they  have   a  high 
contractile  power, 
tary  canal  is  di- 
vided into  various 
special    re- 
gions,     a  s 
pharynx,     cesopha- 
of  gus,     crop,     fore 
stomach  or  gizzard, 

the      giant-crane-   digesting      Stomach, 
fly.  (Photo-micro-  . 

graph  by  Geo.  O.  and  small  and  large  m- 

Mitchell.)  testine.  From  the  canal 

just  at  the  point  of  union  of  the  digesting 
stomach  (ventriculus)  and  the  small  in- 
testine rise  the  so-called  Malpighian 
tubules,  which  are  excretory  organs. 
They  are  long  slender  diverticula  of  the 
alimentary  canal,  and  are  typically  six 

(three  pairs)  in    number.      The  circula-  FlG-  48. —  The  anten- 
na of  a  carrion  bee- 
tory    system   is   composed   of    a  tubular     tie,  with  the  termi- 

vessel  running  longitudinally  through  the 
body  in  the  median  line  just  under  the 
dorsal  wall.  It  is  composed  of  a  series 
of  chambers  or  segmental  parts,  which 
by  a  rhythmic  contraction  and  expansion 
propel  the  blood  anteriorly  and  into  a 
short,  narrow,  unsegmented  anterior  portion  of  the  vessel 


nal  three  segments 
enlarged  and  flat- 
tened, and  bearing 
many  '•  smelling- 
pits/'  the  antenna 
thus  serving  as  an 
olfactory  organ. 
(Photo -micrograph 
by  Geo.  O.Mitchell.) 


BRANCH  ARTHROPOD  A;  CLASS  MSECTA :   THE  INSECTS  185 

which  may  be  called  the  aorta.  There  are  no  other 
arteries  or  veins,  the  blood  simply  pouring  out  of  the 
anterior  end  of  the  dorsal  vessel  into  the  body-cavity.  It 
bathes  the  body  tissues,  flowing  usually  in  regular  channels 
without  walls.  It  re-enters  the  dorsal  vessel  through 
paired  lateral  openings  in  the  chambers. 

The  main  or  central  nervous  system  consists  of  a  large 
ganglion,    the    "brain,"   situated  in  the  head  above  the 


FIG.  49. — A  section  through  the  compound  eye  (in  late  pupal  stage)  of  the 
blow-fly,  Calliphora  romitoria.  In  the  centre  is  the  brain,  with  optic 
loin-,  and  on  the  right-hand  margin  are  the  many  ommatidia  in  longi- 
tudinal section.  (Photo-micrograph  by  Geo.  O.  Mitchell.) 

oesophagus,  which  sends  nerves  to  the  antennae  and  eyes  > 
a  ganglion  in  the  head  below  the  oesophagus  connected 
with  the  brain  by  a  short  commissure  on  each  side  of 
the  oesophagus,  and  sending  nerves  to  the  mouth-parts ; 
and  a  ventral  nerve-chain  composed  of  a  pair  of  longitudinal 


]86  ELEMENTARY  ZOOLOGY 

commissures  lying  close  together  and  running  from  the 
head  to  the  next  to  the  last  abdominal  segment,  which 
bears  a  series  of  segmentally  disposed  ganglia,  each 
ganglion  being  composed  of  two  ganglia  more  or  less 
nearly  completely  fused.  There  is,  in  addition,  a  lesser 
system  called  the  sympathetic  system,  which  comprises  a 
few  small  ganglia  and  certain  nerves  which  run  from 
them  to  the  viscera.  The  function  of  the  nervous  system 
of  insects  reaches  a  very  high  development  among  the 
so-called  "intelligent  insects"  and  certain  extraordi- 
narily complex  and  interesting  instincts  are  possessed  by 
many  forms.  The  social  or  communal  habits  of  the  ants, 
bees,  and  wasps  and  the  habits  connected  with  the  deposi- 
tion of  the  eggs  and  the  care  of  the  young  exhibited  by 
the  digger  wasps  and  other  insects  are  of  extreme 
specialization.  The  organs  of  special  sense  are  highly 
specialized,  the  sense  of  smell  (fig.  48)  reaching  in  par- 
ticular a  high  degree  of  perfec- 
tion. One  of  the  compound  eyes 
(figs.  49  and  50)  may  contain  as 
many  as  30,000  distinct  eye- 
elements  or  ommatidia,  but  the 
sight  is  probably  in  no  insect 
very  sharp  or  clear.  Among 
insects  there  are  organs  of  hear- 
ing of  two  principal  kinds.  In 
FIG.  50. -Part  of  cornea,  snow-  one  kind  the  organ  for  taking  up 

ing  facets,  of  the   compound    ^ie    sound-waves    is    a    PTOUD    of 
eye  of  a  horse-fly  (Therioplec-  •  & 

tes  sp.).     (Photo-micrograph   vibratile  hairs  usually  situated  on 
by  Geo.  O.  Mitchell.)  the  antennJE>  as  js  the  case  with 

the  mosquito;  in  the  other  kind,  it  is  a  stretched  mem- 
brane or  tympanum  such  as  is  found  in  the  fore  leg  of  a 
cricket  or  katydid  or  on  the  first  abdominal  segment  of 
the  locust  (fig.  51) 

The  sexes  are  distinct  in  insects,  and  there  is  often  a 


BRANCH  ARTHROPODA;   CLASS  INSECT  A :    THE  INSECTS   187 

marked  sex  dimorphism ;  in  numerous  species  the  males 
are  winged  while  the  females  are  wingless,  and  in  a  few 
cases  this  condition  is  reversed.  Where  there  is  a 
difference  in  size  between  male  and  female,  the  females 


FIG.  51. — The  auditory  organ  of  a  locust  (Melanoplus  sp.).  The  large  clear 
part  in  centre  of  the  figure  is  the  thin  tympanum,  with  the  auditory 
vesicle  (small  black  pear-shaped  spot)  and  auditory  ganglion  (at  left  of 
vesicle  and  connected  with  it  by  a  nerve)  on  its  inner  surface.  (Photo- 
micrograph by  Geo.  O.  Mitchell.) 


are  usually  the  larger.  Fertilization  of  the  egg  takes 
place  in  the  body  of  the  female  and,  strangely,  this  fertil- 
ization is  effected  after  the  eggshell  has  been  formed.  In 
all  insect  eggs  there  is  a  minute  opening  in  one  pole  of 
the  eggshell  called  the  micropyle  through  which  the 
sperm-cells  enter.  In  a  few  cases  the  young  are  born 
alive,  but  such  a  viviparous  condition  is  exceptional.  In 


i88  ELEMENTARY  ZOOLOGY 

a  few  species,  too,  young  are  produced  parthenogeneti- 
cally,  that  is,  are  produced  from  unfertilized  eggs.  And 
in  the  case  of  a  few  insect  species  male  individuals  are 
not  known. 

Development  and  life-history. — The  young  insect 
when  just  hatched  from  the  egg  either  resembles,  except 
for  the  absence  of  wings,  its  parent  in  general  appearance 
as  in  the  case  of  the  locust,  or  it  may,  as  in  the  butterfly, 
emerge  in  a  form  very  unlike  the  parent.  In  the  first 
case  the  young  has  simply  to  grow,  that  is,  to  increase 


FIG.  52. — The  young  (at  left)  and  adult  (at  right)  of  the  bed-bug,  Acanthia 
lectularia,  a  wingless  insect  with  incomplete  metamorphosis.  (After 
Riley.) 

in  size,  to  develop  wings,  and  to  make  some  other  not 
very  obvious  developmental  changes  in  order  to  become 
fully  grown.  But  in  the  case  of  the  butterfly,  and 
similarly  in  the  case  of  all  other  insects  as  the  flies, 
beetles,  bees  et  aL,  whose  young  hatch  in  a  larval  condi- 
tion differing  markedly  from  the  adult,  some  radical  and 
striking  developmental  changes  occur  before  maturity  is 
reached.  Such  insects  are  said  to  undergo  complete 
metamorphosis  in  their  development,  while  those  insects 
like  the  locusts,  the  sucking-bugs,  white  ants,  and  others, 


BRANCH  ARTHROPODA ;   CLASS  IN  SECT  A :    THE  INSECTS  189 


the  just  hatched  young  of  which  resemble  their  parents, 
are  said  to  have  an  incomplete  metamorphosis  (fig.  52). 

In  the  case  of  insects  with  complete  metamorphosis, 
the  young  hatches  as  an  active  grub  or  worm-like  feeding 
larva  which  increases  in  size,  casting  its  skin  or  molting 
several  times  in  its  growth.  Finally  after  the  last  larval 
molt  (fig.  53)  called  pupation  the  insect  appears  in  a 


FIG.  53. — The  larva  of  the  violet  tip  butterfly,  Polygonia  interragationis* 
making  its  last  molt,  i.e.  pupating.     (Photograph  from  life.) 

quiescent  non-feeding  stage  called  the  pupa  (fig.  54),  and 
encased  in  an  extra  thick  and  firm  chitinous  exoskeleton. 
The  immovable  pupa  is  sometimes  concealed  underground, 
sometimes  enclosed  in  a  silken  cocoon  spun  by  the  larva 
just  before  pupation,  or  is  in  some  other  way  specially 
protected.  It  is  in  this  pupal  condition  that  the  great 
changes  from  wingless,  often  legless,  worm-like  larva  to 


190 


ELEMENTARY  ZOOLOGY 


winged,  six-legged,  graceful  imago  of  adult  stage  are 
completed,  and  with  the  molting  of  the  chitinous  pupal 
cuticle  the  metamorphosis  or  development  of  the  insect 
is  completed.  As  a  matter  of  fact  many  of  the  special 
organs  of  the  adult,  the  legs  and  wings,  for  example, 
begin  to  develop  as  little  buds  or  groups  of  cells  in  the 
body  of  the  larva,  and  when  the  larva  is  ready  to  pupate 


FlG.  54. — Chrysalid  (pupa)  of  the  violet  tip  butterfly,  Polygonia  interraga- 
tionis.  From  this  chrysalid  issues  the  full  fledged  butterfly.  (Photo- 
graph from  life.) 

these  imaginal  wings  and  legs  are  drawn  out  to  the 
external  surface  of  the  body,  and  may  be  readily  recog- 
nized as  they  lie  on  the  ventral  surface  of  the  pupa  folded 
and  closely  pressed  to  the  body  surface.  In  recent  years 
the  study  of  the  post-embryonic  development  of  insects 
with  complete  metamorphosis  has  revealed  some  re- 
markable changes  of  the  internal  organs  which  result  in 
a  nearly  complete  disintegration  or  breaking  down  of 


BRANCH  ARTHROPODA;   CLASS  IN  SECT  A :    THE  INSECTS  191 

most  of  the  internal  organs  of  the  larva  (fig.  55)  and  a 
rebuilding  of  the  organs  of  the  adult  from  primitive  be- 
ginnings. 

The  habits  of  the  larvae  of  insects  with  complete  meta- 
morphosis and  of  the  young  of  some  insects  with  incom- 
plete metamorphosis  often  differ  markedly  from  the 


FIG.  55. — A  cross-section  of  the  body  of  the  pupa  of  a  honey-bee,  showing 
the  body  cavity  filled  with  disintegrated  tissues,  and  (at  the  bottom)  a 
budding  pair  of  legs  of  the  adult,  the  larva  being  wholly  legless. 
(Photo-micrograph  by  Geo.  O.  Mitchell.) 

habits  of  the  adults,  and  as  the  habits  and  instincts  of 
insects  are  remarkably  specialized,  the  study  of  their  be- 
havior and  of  the  structural  and  physiological  modifica- 
tion which  their  varied  habits  of  life  have  brought  about 
is  of  much  interest  and  significance.  In  later  paragraphs 
this  phase  of  insect  study  will  be  again  referred  to. 

Classification. — Much  attention  has  been  paid  to  the 
classification  of  insects  and  the  300,000  (approximately) 
known  species  have  been  variously  grouped  together  into 
orders  by  different  entomologists.  A  subdivision  of  the 
class  Insecta  into  five  orders  was  proposed  by  Linnaeus 
about  1750  and  was  used  until  comparatively  recently. 
Since  then,  however,  numerous  other  arrangements  have 
been  proposed,  all  of  them  agreeing  in  increasing  the 


I92  ELEMENTARY  ZOOLOGY 

number  of  orders  by  breaking  up  some  of  the  old  ones 
into  two  or  more  new  ones.  The  classification  adopted 
in  the  text-book  *  of  zoology  which  we  have  made  our 
reference  in  classification  is  an  8-order  system.  The 
latest  English  t  text-book,  in  entomology  adopts  a 
9-order  system,  while  the  principal  American  J  text-book 
on  this  subject  divides  the  insects  into  nineteen  orders. 

The  classification  depends  chiefly  on  the  character  of 
the  post-embryonic  development,  that  is,  on  whether  the 
metamorphosis  is  complete  or  incomplete,  and  on  the 
structural  character  of  the  mouth-parts  and  wings.  In 
the  following  paragraphs  a  few  of  the  larger  insect  orders, 
with  some  special  representatives  of  each,  will  be  briefly 
considered. 

The  best  American  text-book  of  the  classification  and 
habits  of  insects  is  Comstocks'  "Manual  of  Insects." 
For  an  account  of  the  structure  of  the  wings  and  mouth- 
parts  of  various  insects  see  Comstock  and  Kellogg 's 
"  Elements  of  Insect  Anatomy." 

Orthoptera  :  the  locusts,  cockroaches,  crickets,  katy- 
dids, etc. — TECHNICAL  NOTE. — Obtain  specimens  of  crickets  or 
katydids,  and  cockroaches,  and  compare  the  external  body  struc- 
ture with  that  of  the  grasshopper;  examine  especially  the  wings, 
mouth-parts,  legs,  and  egg-laying  organs.  Note  that  the  hindmost 
legs  of  the  cockroach  are  not  fitted  for  leaping  but  for  running.  Note 
the  sound-making  (stridulating)  organs  on  the  bases  of  the  fore  wings 
of  the  male  katydids  and  crickets.  Note  the  auditory  organs  (tym- 
pana) in  the  fore  tibiae  of  the  katydids  and  crickets.  Crickets  can 
be  easily  kept  alive  in  breeding-cages  in  the  laboratory  and  their 
feeding  habits  and  much  of  their  life-history  observed.  The  growth 
of  the  young  and  the  development  of  the  wings  can  be  noted,  and 
will  be  found  to  be  essentially  similar  to  the  conditions  already 
found  in  the  case  of  the  locust. 

The  locust  studied  as  one  of  the  examples  of  the  class 
Insecta  belongs  to  the  order  Orthoptera,  which  also  in- 

*  A  Text-book  of  Zoology,  Parker  &  Haswell,  1897. 

f  The  Cambridge  Natural  History,  vol.  V,  1895.  vol.  VI,  1899. 

|  A  Manual  for  the  Study  of  Insects,  J.  H.  and  A.  B.  Comstock,  1897. 


BRANCH  ARTHROPODA;   CLASS  1NSECTA :    THE  INSECTS  *93 

eludes  the  cockroaches,  crickets  (fig.  56),  katydids  and 
green  grasshoppers,  the  walking-stick  or  twig  insects,  the 
praying  mantis  and  others. 
The  members  of  this  order  all 
have  an  incomplete  metamor- 
phosis, and  in  all  the  mouth- 
parts  are  fitted  for  biting  and 
the  fore  wings  are  more  or 
less  thickened  and  modified  to 
serve  as  covers  or  protecting 
organs  for  the  broad,  plaited, 
membranous  hind  wings,  which 
are  the  true  flight  organs.  The 
hind  legs  of  locusts,  grasshop-  FIG.  56. —The  house  cricket, 
pers,  crickets,  and  katydids  are  ™^) and  female  (*)•  (From 
very  large,  and  enable  the  in- 
sects to  leap;  the  legs  of  the  cockroaches  are  fitted  for 
swift  running;  the  fore  legs  of  the  praying  mantis  are 
fitted  for  grasping  other  insects  which  serve  as  their  food, 
and  the  legs  of  the  walking-stick  (fig.  162)  are  long  and 
slender  and  fitted  for  slow  walking.  The  shrill  singing  of 
the  crickets  and  katydids  and  the  loud  "clacking"  of 
the  locusts  are  all  made  by  stridulation,  that  is,  by 
rubbing  two  roughened  parts  of  the  body  together.  The 
sounds  of  insects  are  not  made  by  vocal  cords  in  the 
throat.  The  male  crickets  and  katydids  (for  only  the 
males  sing)  have  the  veins  of  the  fore  wings  modified  so 
that  when  the  bases  of  the  wings  are  rubbed  together 
(and  when  the  cricket  or  katydid  is  at  rest  the  base  of 
one  fore  wing  overlaps  the  base  of  the  other)  a  part  of 
one  wing  called  the  ' '  scraper  ' '  rubs  against  a  part  of  the 
other  called  the  "file"  and  the  shrilling  is  produced. 
The  sounds  of  locusts  are  produced  by  the  rubbing  of 
the  inside  of  the  hind  leg  against  the  outside  of  the  fore 
wing  when  the  insect  is  at  rest,  or  by  striking  the  front 


i94 


ELEMENTARY  ZOOLOGY 


margin  of  each  hind  wing  against  the  hind  margin  of  each 
fore  wing  when  the  locust  is  flying.  For  hearing  the 
Orthoptera  are  provided  with  auditory  organs  having  the 
character  of  tympana  or  vibrating  membranes.  In  the 
locusts  these  ears  (fig.  51)  are  situated  on  the  dorsal 
surface  of  the  first  abdominal  segment;  in  the  katydids 
and  crickets  they  are  in  the  tibiae 
of  the  fore  legs.  The  food  of 
locusts,  crickets,  and  katydids  is 
vegetable,  being  usually  green 
leaves ;  the  cockroaches  eat  either 
plant  or  animal  substances  fresh 
or  dry,  while  the  praying  mantis 
is  predaceous,  feeding  on  other 
insects  which  it  catches  in  its 
strong  grasping  fore  legs.  The 
walking-stick  or  twig  insect  is  an 
excellent  example  of  what  is  called 
1 '  protective  resemblance  ' '  among 
animals.  Indeed  most  of  the 
FIG.  57.— A  bird  louse,  Mr-  Orthoptera  are  so  colored  and 

mus  prcest  an  s,  irom  a  tern, 

Sterna  maxima.  Most  birds  patterned  as  to  be  almost  indistin- 
w^nglest^bitin'g11  inlets!  guishable  when  on  their  usual  rest- 
called  bird-lice,  which  are  ing-  or  feeding-grounds.  Some 

external   parasites  feeding       ,    .,  .     ^   ,. 

on  the  feathers  of  the  bird  °f  the  tropical  Orthoptera  carry 
host.  The  bird  louse  to  a  marvelous  degree  this  modi- 
figured  is  about  TV  in.  long.  -..''/•'• 

(Photo-micrograph by  Geo.  fication  for  the  sake  of  protection. 
O.  Mitchell.)  £jn  this  connection  read  Chapter 

XXXI    referring  to  '•  Protective  Resemblances  ".) 

Odonata  and  Ephemerida  :  the  dragon-flies  and  May- 
flies.— TECHNICAL  NOTE. — Obtain  specimens  of  adult  and  imma- 
ture dragon-flies.  The  young  dragon-flies  (fig.  59)  may  be  got  by 
raking  out  some  of  the  slime  and  aquatic  vegetation  from  the  bottom 
of  a  small  pond.  Compare  the  external  structure  of  the  adult  dragon- 
flies  with  that  of  the  grasshopper  ;  note  the  large  eyes,  the  narrow 
nerve-veined  wings,  the  biting  mouth-parts,  and  the  short  antennae. 


BRANCH  ARTHROPODA ;   CLASS  INSECT  A :    THE  INSECTS  *95 

Compare  the  young  dragon-flies  with  the  adults  ;  note  the  devel- 
oping wings  and  the  peculiar  modification  of  the  lower  lip  into  a 
protrusible,  grasping  organ  which  when  at  rest  is  folded  like  a  mask 
over  the  face.  Examine  the  interior  of  the  posterior  part  of  the 
alimentary  canal  to  find  the  rectal  gills.  Obtain  specimens  of  adult 
and  young  May-flies.  The  young  may  be  found  on  the  under  side 
of  stones  in  a  "  riffle  "  in  almost  any  stream.  They  live  also  in  ponds. 
They  may  be  recognized  by  reference  to  fig.  61.  Compare  adult 
May-flies  with  the  dragon-flies  ;  note  the  weakly  chitinized,  delicate 
body-wall,  and  the  difference  in  size  between  fore  and  hind  wings  ; 
note  the  biting  mouth-parts  of  the  young  and  their  absence  or 
presence  in  vestigial  condition  only  in  the  adults. 

The  young  of  both  dragon-flies  and  May-flies  may  easily  be  kept 
alive  in  the  laboratory  aquarium  (fruit-jars  or  battery-jars  with  pond 
water  in),  and  their  feeding  habits,  their  swimming,  their  respiration, 
and  much  of  their  development  observed.  The  young  May-flies 
should  be  got  from  ponds,  not  running  streams.  Put  one  ot  these 
semi-transparent  May-fly  nymphs  into  a  watch-glass  of  water,  and 
examine  under  the  microscope.  The  movements  of  the  gills,  heart, 
and  alimentary  canal,  and  much  of  the  anatomy  can  be  readily  made 
out.  The  emergence  of  the  adult  from  the  nymphal  skin  can  be 
seen  if  close  watch  is  kept.  The  young  dragon-flies  may  be  seen  to 
capture  and  devour  their  prey.  They  may  also  transform  into  adults, 
but  for  this  it  will  be  necessary  to  obtain  nymphs  nearly  ready  for 
transformation. 

Among  the  most  familiar  and  interesting  insects  are  the 
dragon-flies  (fig.  58),  sometimes  called  "devil's  darning- 
needles."  They  are  commonly  seen  flying  swiftly  about 
over  ponds  or  streams  catching  other  flying  insects.  The 
dragon-flies  are  the  insect-hawks ;  they  are  predaceous  and 
very  voracious,  and  are  probably  the  most  expert  flyers 
of  all  insects.  There  are  many  species,  and  their  bright 
iridescent  colors  and  striking  wing-patterns  make  them 
very  beautiful.  The  young  dragon-flies  (fig.  59)  are 
aquatic,  living  in  streams  and  ponds,  where  they  feed 
on  the  other  aquatic  insects  in  their  neighborhood. 
They  catch  their  prey  by  lying  in  wait  until  an  insect 
comes  close  enough  to  be  reached  by  the  extraordi- 
narily developed  protrusible  grasping  lower  lip  (fig.  60). 
When  at  rest  this  lower  lip  lies  folded  on  the  face  so  as 
to  conceal  the  great  jaws.  The  young  dragon-flies  breathe 


196 


ELEMENTARY  ZOOLOGY 


by  means  of  gills  which  do  not  project  from  the  outside 
of  the  body,  as  do  the  gills  of  other  aquatic  insects,  but 
line  the  inner  wall  of  the  posterior  or  rectal  part  of  the 


FIG.  58. — A  dragonfly.  Sympetrum  FIG.  59. — The  young  (nymph)  of  the 
illotum,  common  in  California.  dragon-fly,  Sympetrum  illotum. 
(From  life.)  (From  Jenkins  and  Kellogg.) 

alimentary  canal.  Water  enters  the  canal  through  the 
anal  opening  and  bathes  these  gills,  bringing  oxygen  to 
them  and  taking  away  carbonic  acid  gas.  The  aquatic 


FlG.  60. — Young  (nymph)   dragon-fly,    showing  lower  lip  folded  and  ex- 
tended.     (F_rom  Jenkins  and  Kellogg.) 

immature  life  of  the  dragon-flies  lasts  from  a  few  months 
to  two  years.  When  ready  to  change  to  adult,  the  young 
crawls  out  of  the  water  and  clinging  to  a  rock  or  plant 
makes  its  last  molt. 


BRANCH  ARTHROPOD  A;   CLASS  INSECT  A :    THE  INSECTS  197 


Other  abundant  and  interesting  pond  and  brook  insects 
are  the  May-flies.  The  young  May-flies  (fig.  61)  are 
aquatic,  living  in  streams  and 
ponds  and  feeding  on  minute 
organisms  such  as  diatoms  and 
other  algae.  The  immature  life 
lasts  a  year,  or  even  two  or  three 
in  some  species,  and  then  the 
May-fly  crawls  out  of  the  water 
upon  a  plant-stem  or  projecting 
rock  and,  molting,  appears  as  the 
winged  adult.  The  adult  May- 
fly, having  its  mouth-parts  atro- 
phied (a  few  May-flies  have  func- 
tional mouth-parts), takes  no  food, 
and  lives  only  a  few  hours  or  at 
most  perhaps  a  few  days.  It  has 
the  shortest  life  (in  adult  stage) 
of  all  insects.  The  female  drops 
her  eggs  into  the  water. 

Hemiptera :  the  sucking- bugs. 

— TECHNICAL     NOTE. — Obtain  speci- 


FIG.  61. — Young  (nymph)  of 
May-fly,  showing  (g)  tra- 
cheal  gills.  (From  Jenkins 
and  Kellogg.) 


mens  of  water-striders  (narrow  elongate-bodied  insects  with  long 
spider-like  legs  which  run  quickly  about  on  the  surface  of  ponds 
or  quiet  pools  in  streams),  water-boatmen  (mottled  grayish  insects 
about  half  an  inch  long  which  swim  and  dive  about  in  ponds  and 
stream-pools),  back-swimmers  (which  are  usually  in  company  with 
the  water-boatmen,  but  which  swim  with  back  downwards  and  • 
are  marked  with  purplish-black  and  creamy  white  patches),  cicadas 
(the  dog-day  locusts),  and  plant-lice  (the  ••  green  fly  "of  rose-bushes 
and  other  cultivated  plants).  Compare  the  external  structure  of 
some  of  these  Hemiptera  with  the  other  insects  already  examined  ; 
note  especially  the  sucking  beak,  composed  of  the  elongate  tube- 
like  labium  in  which"  lie  the  greatly  modified  flexible  needle-like 
maxillae  and  mandibles,  the  whole  forming  an  equipment  for  pierc- 
ing and  sucking.  Obtain  immature  specimens  of  some  of  these 
insects  (distinguished  by  their  smaller  size  and  the  wing-pads)  ;  note 
that  the  metamorphosis  is  incomplete,  the  young  resembling  the 
parents  in  general  appearance.  Both  immature  and  adult  specimens 
of  water-boatmen (Corisa),  back-swimmers  (Notonecta),  and  water- 


198 


ELEMENTARY  ZOOLOGY 


striders  (Hygrotrechus}  can  be  easily  kept  in  the  laboratory  aquaria- 
and  their  swimming,  breathing,  and  feeding  habits  observed.  Note 
especially  the  carrying  of  air  down  beneath  the  water. 

The  Hemiptera  are  characterized  particularly  by  their 
highly  specialized  sucking  mouth-parts,  no  other  of  the 
sucking  insects  having  the  proboscis  composed  in  the 


FIG.  62. — The  female  red  orange  scale 
insect,  Aspidiotus  aurantii,  very  injuri- 
ous to  orange-trees.  It  has  no  wings, 
legs,  nor  eyes,  but  remains  motionless 
on  a  leaf,  stem,  or  fruit,  holding  fast  by 
its  long  slender  beak,  through  which  it 
sucks  up  the  plant-sap.  The  male  is 
winged,  and  has  no  mouth-parts,  taking 
no  food.  (Photo-micrograph  by  Geo. 
O.  Mitchell.) 


FIG.  63. — The  female  rose- 
scale,  Diaspis  rosa,  a 
pest  of  rose-bushes,  with- 
out eyes,  wings,  or  legs, 
but  with  slender  sucking 
proboscis.  The  male  is 
winged  and  without 
mouth-parts.  (Photo-mi- 
crograph by  Geo.  C). 
Mitchell.) 


same  manner.  The  palpi  of  both  maxillae  and  labium 
are  wholly  wanting  in  Hemiptera  and  the  flexible  needle- 
like  maxillae  and  mandibles  are  enclosed  in  the  tubular 
labium.  This  order  is  a  large  one  and  includes  many 
well-known  injurious  species,  as  the  chinch-bug  (Blissns 
leucopterus),  which  occurs  in  immense  numbers  in  the 
grain-fields  of  the  Mississippi  valley,  sucking  the  juices 
from  the  leaves  of  corn  and  wheat,  the  grape  Phylloxera 
(Phylloxera  vastatrix),  so  destructive  to  the  vines  of 
Europe  and  California,  the  scale  insects  (Coccidce]  (figs. 


BRANCH  ARTHROPODA;   CLASS  INSECT  A :   THE  INSECTS  199 

62  and  63),  the  worst  insect  pests  of  oranges,  the  squash- 
bugs  and  cabbage-bug  and  a  host  of  others.  Some  of 
the  Hemiptera,  for  example,  the  lice  and  bed-bugs,  are 
predaceous,  sucking  the  blood  of  other  animals. 

The  water-striders  (fig.  64)  catch  other  insects,  both 
those  that  live  in  the  water 
and  those  which  fall  on  to 
its  surface,  and  holding  the 
prey  with  their  seizing 
fore  legs  they  pierce  its 
body  with  their  sharp 
beak  and  suck  its  blood. 
They  lay  their  eggs  in  the 
spring  glued  fast  to  water- 
plants.  The  young  water- 
striders  are  shorter  and 
stouter  in  shape  than  the 
adults. 

The      Water-boatmen    FIG.  64. — A  water-strider,  Hygrotrechns 
(fig.  65)  and  back-swim-          SP"     (F-m  Jenkins  and  Kellogg., 
mers  swim   and   dive  about  in  the  water,   coming  more 
or   less   frequently  to  the  surface  to  get  a  supply  of  air. 

This  air  they  hold  under  the 
wings,  or  on  the  sides  and 
under  part  of  the  body  en- 
tangled in  the  fine  hairs  on 
the  surface.  The  insects 
appear  to  have  silvery  spots 
on  the  body,  due  to  the 
presence  of  this  air.  The 

FIG.   65. — A  water-boatman,   Corisa*  "rowing  "  legs  of  the  water- 
sp.     (From  Jenkins  and  Kellogg.,       boatmen      (Corisd]     are     the 

hindmost  pair;  in  the  back-swimmers  (Notonecta)  they 
are  the  middle  legs. 

The  cicadas  (fig.  66)  are  the  familiar  insects  of  summer 


20O 


ELEMENTARY  ZOOLOGY 


which  sing  so  shrilly  from  the  trees,  the  seventeen-year 
cicada    (Cicada    septendecini)    (oftentimes    called    locust) 

being  the  best  known  of 
this  family.  Its  eggs 
are  laid  in  slits  cut  by 
the  female  in  live  twigs. 
The  young,  which  hatch 
in  about  six  weeks,  do 
not  feed  on  the  green 
foliage,  but  fall  to  the 
ground,  burrow  down  to 
the  roots  of  the  tree  and 
there  live,  sucking  the 
juices  from  the  roots,  for 

FIG.   66. — The  seventeen-year  cicada,    Ci-   sixteen  years  and  ten  or 
cada   septendecim ;   the   specimen  at  left      ,  ,,  iiru 

showing  sound-making  organ, «,./.,  ven-  eleven  months.      When 

tral  plate;   /,  tympanum.      (From   speci-   about  to  become    adult, 
men.) 

the  young  cicada  crawls 

up  out  of  the  ground  and  clinging  to  the  tree-trunk  molts 
for  the  last  time,  and  flies  to  the  tree-tops. 

The  plant-lice  (Aphididce)  are  small  soft-bodied 
Hemiptera  which  have  both  winged  and  wingless  indi- 
viduals. In  the  early  spring  a  wingless  female  hatches 
from  an  egg  which,  laid  in  the  preceding  fall,  has  passed 
the  winter  in  slow  development.  This  wingless  female, 
called  the  stem-mother,  lays  unfertilized  eggs  or  more 
often  perhaps  gives  birth  to  live  young,  all  of  which  are 
similarly  wingless  females  which  reproduce  partheno- 
genetically.  This  reproduction  goes  on  so  rapidly  that 
the  plant-lice  become  overcrowded  on  the  food-plant  and 
then  a  generation  of  winged  *  individuals  is  produced  from 

*  It  has  been  shown  by  experiment  that  the  winged  individuals,  which  are 
able  to  leave  the  old  food-plant  and  scatter  over  new  plants,  do  not  appear 
until  the  food-supply  begins  to  run  short.  At  the  insectary  of  Cornell  Uni- 
versity ninety -four  successive  generations  of  wingless  individuals  were  bred, 


BRANCH  ARTHROPODA;  CLASS  JNSECTA :   THE  INSECTS  201 

time  to  time.  These  winged  plant-lice  fly  away  to  new 
plants.  In  the  autumn  a  generation  of  males  and  females 
is  produced ;  these  individuals  mate  and  each  female  lays 
a  single  large  egg  which  goes  over  the  winter,  and  pro- 
duces in  the  spring  the  wingless  agamic  stem-mother. 
Plant-lice  produce  honey-dew,  a  sweetish  substance  much 
liked  by  ants,  and  the  lice  are  often  visited,  and  sometimes 
specially  cared  for,  by  the  ants  for  the  sake  of  this  honey- 
dew.  Small  as  they  are,  plant-lice  occur  in  such  numbers 
as  to  do  great  damage  to  the  plants  on  which  they  feed. 
The  apple-aphis,  cherry-aphis,  pear-aphis,  cabbage-aphis 
and  others  are  well-known  pests.  The  most  notoriously 
•  destructive  plant-louse  is  the  grape  PJiylloxera,  which 
lives  on  the  roots  and  leaves  of  the  grape-vine.  Im- 
mense losses  have  been  caused  by  this  pest,  especially  in 
the  wine-producing  countries  of  southern  Europe. 

Diptera  :  the  flies. — TECHNICAL  NOTE. — Obtain  specimens 
of  the  adult  and  young  stages  of  the  blowfly  and  the  mosquito.  All 
the  young  stages  of  the  blowfly  may  be  obtained,  and  its  life-history 
studied,  by  exposing  a  piece  of  meat  to  decay  in  an  open  glass  jar. 
The  larvae  of  the  mosquito  are  the  familiar  wrigglers  of  puddles 
and  ponds,  and  by  collecting  some  of  them  and  keeping  them  in  a 
glass  jar  of  water  covered  with  a  bit  of  mosquito-netting,  the  life- 
history  of  the  mosquito  is  easily  studied.  If  the  eggs  can  be  ob- 
tained from  the  pond  so  much  the  better ;  they  are  in  little  black 
I  masses  floating  on  the  surface  of  the  water,  and  resemble  at  first 
j  glance  nothing  so  much  as  a  floating  bit  of  soot.  The  external 
structure  of  the  adult  flies  should  be  compared  with  that  of  the 
other  insects  studied,  noting  especially  the  condition  of  mouth-parts 
and  wings,  and  the  substitution  of  balancers  for  the  hind  wings. 
The  mouth-parts  of  the  mosquito  are  in  the  form  of  a  long  proboscis 
composed  of  six  slender  needle-like  stylets  lying  in  a  tube  narrowly 
open  along  its  dorsal  surface.  The  tube  is  the  labium,  and  the 
stylets  are  the  two  maxillae,  two  mandibles,  and  two  other  parts 
known  as  the  epipharynx  and  the  hypopharynx.  Two  additional 
thicker  elongate  segmented  processes  lying  outside  of  and  parallel 
with  the  tube  are  the  maxillary  palpi.  The  male  mosquito  (distin- 
guished from  the  female  by  the  more  hairy  or  bushier  antennae)  lacks 

In  taking  care  to  provide  a  constantly  abundant  supply  of  food.     This  ex 
it  was  continued  for  more  than  lour  years. 


202  ELEMENTARY  ZOOLOGY 

the  pair  of  needle-like  mandibles.  The  mouth-parts  of  the  blowfly 
are  composed  almost  exclusively  of  the  thick  fleshy  proboscis-like 
labium,  which  is  expanded  at  the  tip  to  form  a  rasping  organ 

The  Diptera  or  true  flies  are  readily  distinguishable 
from  other  insects  by  their  having  a  single  pair  of  wings 
instead  of  two  pairs,  the  hind  wings  being  transformed 
into  small  knob-headed  pedicels  called  balancers  or 
halteres.  The  flies  undergo  complete  metamorphosis, 
and  their  mouth-parts  are  fitted  for  piercing  and  sucking 
(as  in  the  mosquito)  or  for  rasping  and  lapping  (as  in  the 
blowfly).  Nearly  50,000  species  of  flies  are  known,  more 
than  4,000  being  known  in  North  America  alone. 

The  blowfly  (CallipJiora  vomitoria)  is  common  in 
houses,  but  can  be  distinguished  from  the  house-fly  by  its 
larger  size  and  its  steel-blue  abdomen.  It  lays  its  eggs 
on  decaying  meat  (or  other  organic  matter)  and  the  white 
footless  larvae  (maggots)  hatch  in  about  twenty-four 
hours.  They  feed  voraciously  and  become  full  grown  in 
a  few  days.  They  then  change  into  pupae  which  are 
brown  and  seed-like,  being  completely  enclosed  in  a  uni- 
form chitinized  case  which  wholly  conceals  the  form  of  the 
developing  fly.  The  house-fly  has  a  life-history  and  im- 
mature stages  like  the  blowfly,  but  its  eggs  are  deposited 
on  manure. 

The  mosquito  (Culcx  sp.)  (fig.  67)  lays  its  eggs  in  a 
sooty-black  little  boat-shaped  mass  which  floats  lightly  on 
the  surface  of  the  water.  In  a  few  days  the  larvae,  or 
"  wrigglers,"  issue  and  swim  about  vigorously  by  bend- 
ing the  body.  The  head  end  of  the  body  is  much  broader 
than  the  other,  the  thoracic  segments  being  markedly 
larger  than  the  abdominal  ones.  The  head  bears  a  pair 
of  vibrating  tufts  of  hairs,  which  set  up  currents  of  air  that 
bring  microscopic  organic  particles  in  the  water  into  the 
wriggler's  mouth.  At  the  posterior  tip  of  the  body  are 
two  projections,  one  the  breathing-tube  (the  wriggler 


BRANCH  ARTHROPODS;   CLASS  1NSECTA :    THE  INSECTS  2°3 


coming  often  to  the  surface  to  breathe),  and  the  other 
the  real  tip  of  the  abdomen.  The  wriggler,  although 
heavier  than  water,  can  hang  suspended  from  the  surface 
film  by  the  tip  of  its  breathing-tube.  It  changes  in  a  few 


FIG.  67. — The  mosquito,  Culex  sp. ;  showing  eggs  Con  surface  of  water), 
larvae  (long  and  slender,  in  water),  pupa  (large  headed,  at  surface), 
and  adult  (in  air).  (From  living  specimens.) 


204 


ELEMENTARY  ZOOLOGY 


change  to  the  adult  mosquito  the  pupa  (which,  unlike  the 
wriggler,  is  lighter  than  water)  floats  at  the  surface  of  the 
water,  back  uppermost.  The  chitinous  cuticle  splits 
along  the  back  and  the  delicate  mosquito  comes  out,  rests 


FIG.  68. — The  house-flea,  Pulex  irritans;  a,  larva;  £,  pupa;  t,  adult. 
(The  fleas  are  probably  more  nearly  related  to  the  Diptera  than  to  any 
other  order  of  insects.  (After  Beneden.) 


on  the  floating  pupal  skin  until  its  wings  are  dry,  and 
then  flies  away.  Only  the  female  mosquitoes  suck  blood. 
If  they  cannot  find  animals,  mosquitoes  live  on  the  juices 
of  plants.  They  are  world-wide  in  their  distribution, 
being  serious  pests  even  in  Arctic  regions,  where  they  are 
often  intolerably  numerous  and  greedy.  Recent  investi- 
gations have  shown  that  the  germs  which  cause  malaria 
in  man  live  also  in  the  bodies  of  mosquitoes,  and  are  in- 
troduced into  the  blood  of  human  beings  by  the  biting 


BRANCH  ARTHROPODA;   CLASS   IN  SECT  A :   THE  INSECTS  205 

(piercing)  of  the  mosquitoes.  It  is  probable  also  that  the 
germs  of  yellow  fever  are  distributed  by  mosquitoes  in  the 
same  way.  By  pouring  a  little  kerosene  on  the  surface 
of  a  puddle  no  mosquitoes  will  be  able  to  escape  from 
the  water. 


Lepidoptera:  the  moths  and  butterflies. — TECHNICAL 

NOTE. — Obtain  specimens  of  a  few  moths,  and  compare  with  the 
butterfly  already  studied  ;  note  especially  the  character  of  antennae. 
Obtain  miscellaneous  specimens  of  larvae,  pupae,  and  cocoons  of  any 
moths  or  butterflies.  Note  the  variety  in  colors,  markings,  and 
skin  covering's  of  the  larvae  ;  note  the  shape  and  markings  of  the 
pupae.  Rear  from  eggs,  larvae,  or  pupae  in  breeding-cages  any 
moths  and  butterflies  obtainable  (for  directions  for  rearing  moths 
and  butterflies  see  Chapter  XXXIV),  keeping  note  of  the  times  of 
molting  and  of  the  duration  of  the  various  immature  stages.  If 
the  eggs  of  silkworms  can  be  obtained  the  whole  life  cycle  of  the 
silkworm  moth  can  be  observed  in  the  schoolroom.  The  larvae 
(worms)  feed  on  mulberry  or  osage  orange  leaves,  feeding  vora- 
ciously, growing  rapidly  and  making  no  attempts  to  escape.  The 
molting  of  the  larvae  can  be  observed,  the  spinning  of  the  silken 
cocoon,  and  the  final  emergence  of  the  moth.  The  moths  after 
emergence  will  not  fly  away,  but  if  put  on  a  bit  of  cloth  will  mate, 
and  lay  their  eggs  on  it.  From  these  eggs,  which  should  be  kept 
well  aired  and  dry,  larvae  will  hatch  in  nine  or  ten  months  (if  the 
race  is  an  "  annual  "). 


The  Lepidoptera  (figs.  69-74)  include  all  those  insects 
familiarly  known  to  us  as  moths  and  butterflies ;  they  are 
characterized  by  their  scale-covered  wings  (fig.  69)  and 
long  nectar-sucking  proboscis  composed  of  the  two  inter- 
locking maxillae.  They  undergo  a  complete  metamorpho- 
sis (fig.  70)  and  their  larvae  are  the  familiar  caterpillars  of 
garden  and  field.  These  larvae  have  biting  mouth-parts 
and  feed  on  vegetation,  some  of  them  being  very  injurious, 
for  example  the  army-worms,  cut-worms,  codlin  moth 
worms,  etc.  The  adult  moths  and  butterflies  take  only 
liquid  food,  or  no  food  at  all,  and  are  wholly  harmless  to 
vegetation.  The  structure  and  life-history  of  a  butterfly 
has  already  been  studied,  and  in  the  more  general  condi- 


206  ELEMENTARY  ZOOLOGY 

tions  of  structure  and  life-history  there  is  much  similarity 
in  the  many  insects  of  this  order.  The  eggs  are  usually 
laid  on  the  food-plant  of  the  larva ;  the  larva  feeds  on  the 


FIG.  69. — A  small,  partly  denuded  part,  much  magnified,  of  a  wing  of  a 
"  blue"  butterfly,  Lyceena  sp.,  showing  the  wing,scales  and  the  pits  in 
the  wing-membrane,  in  which  the  tiny  stems  of  the  scales  are  inserted. 
(Photo-micrograph  by  Geo.  O.  Mitchell.) 

leaves  of  this  plant,  grows,  molts  several  times,  and 
pupates  either  in  the  ground  or  in  a  silken  cocoon  or 
simply  attached  to  a  branch  or  leaf.  There  are  about 
six  thousand  species  of  moths  and  butterflies  known 
in  North  America,  and  they  are  our  most  beautiful  in- 
sects. 


Coleoptera  :  the  beetles. — TECHNICAL  NOTE.  — Obtain 
specimens  of  various  beetles,  among  them  some  water-beetles  and 
June-beetles  with  their  young  stages,  if  possible  ;  if  not,  then  the 
young  stages  and  adults  of  any  beetle  common  in  the  neighborhood 
of  the  school.  Of  the  swimming  and  diving  water-beetles  there  are 
three  families,  viz.,  the  Gyrinida?  or  whirligig  beetles,  with  four  eyes 
(each  compound  eye  divided  in  two),  the  Hydrophilidas,  or  water- 
scavengers  with  two  eyes  and  antennas  with  the  terminal  segments 


BRANCH  ARTHROPOD/1;   CLASS  IN  SECT  A :   THE  INSECTS  207 

thicker  than  the  others,  and  the  Dytiscidae  or  predaceous  water- 
beetles  with  two  eyes  and  slender  thread-like  antennae.  Try  to 
find  Dytiscidae,  large,  oval,  shining  black  beetles  ;  the  larvae  are 
called  water-tigers  and  are  long,  slim,  active  creatures  with  six  legs 


FlG.  70.  —  The  forest  tent-caterpillar  moth,  Clisiocampa  disstria,  in  its 
various  stages;  m,  male  moth;  /",  female  moth;  />,  pupa;  e,  eggs  (in  a 
ring)  recently  laid;  g.  eggs  hatched;  r,  larva  or  caterpillar.  Moths 
and  caterpillar  are  natural  size,  eggs  and  pupa  slightly  enlarged. 
(Photograph  by  M.  V.  Slingerland. ) 


and  slender  curving  jaws  (see  fig.  76).  The  June-beetles  are  the 
heavy  brown  buzzing  "June-bugs"  and  their  larvae  are  the  common 
"white  grubs  "found  underground  in  lawns  and  pastures.  Have 
live  water-tigers  and  predaceous  water-beetles  in  the  aquarium. 
Note  their  feeding  and  breathing.  Compare  the  external  structure 
of  the  beetles  with  that  of  the  other  insects,  noting  especially  the 
biting  mouth-parts,  and  their  thickened  horny  fore  wings  serving 
as  covers  for  the  folded  membranous  hind  wings. 


208  ELEMENTARY  ZOOLOGY 

The  Coleoptera  is  the  largest   insect  order,   probably 
100,000  species  of  beetles  being  known,  of  which  10,000 


FIG.  71. — A  trio  of  apple  tent-caterpillars,  Ctisiocampa  americana,  natural 
size.  These  caterpillars  make  the  large  unsightly  webs  or  ;i  tents  "  in 
apple-trees,  a  colony  of  the  caterpillars  living  in  each  tent.  (Photograph 
from  life  by  M.  V.  Slingerland.) 

species  are  found  in  North  America.  They  pass  through 
a  complete  metamorphosis  (figs.  75  and  76),  the  larvse  of 
the  various  kinds  showing  much  variety  in  form  and  habit. 


BRANCH  ARTHROPODA;   CLASS  IN  SECT  A :    THE  INSECTS  209 

The  pupae  are  quiescent  and  are  mummy-like  in  appear- 
ance, the  legs  and  wings  being  folded  and  pressed  to  the 
ventral  surface  of  the  body.  Among  the  familiar  beetles 
are  the  lady-birds,  which  are  beneficial  insects  feeding  on 
plant-lice  and  other  noxious  forms ;  the  beautifully  colored 


FIG.  72.—  A.  family  of  forest  tent-caterpillars  (Clisiocampa  disstria  ,  resting 
during  the  day  on  the  bark,  about  one-third  natural  size.  (Photograph 
from  life  by  M.  V.  Slingerland.) 

tiger-beetles,  predaceous  in  habit;  the  "tumblebugs  "  and 
carrion  beetles,  which  feed  on  decaying  organic  matter; 
the  luminous  fire-flies  with  their  phosphorescent  organs 
on  the  ventral  part  of  the  abdomen;  the  striped  Colorado 
potato-beetle  and  the  cucumber-beetles  and  numerous 
other  destructive  leaf-eating  kinds;  the  various  weevils 


210 


ELEMENTARY  ZOOLOGY 


(fig.  78)  that  bore  into  fruits,  nuts  and  grains,  and  the 
many  wood-boring  beetles,  destructive  to  fruit-trees  as 
well  as  to  shade-  and  forest-trees. 

The  predaceous  water-beetles  (Dyticus  sp. )  are  common 
in  ponds  and  quiet  pools  in  streams.  When  at  rest  they 
hang  head  downward  with  the  tip  of  the  abdomen  just 
projecting  from  the  water.  Air  is  taken  under  the  tips  of 


FIG.  7v—  Moths  of  the  peach-tree  borer,  Sanninoidea  exitiosa,  natural  size; 
the  upper  one  and  the  one  at  the  right  are  females.  (Photograph  by 
M.  V.  Slingerland.) 

the  folded  wing-covers  (elytra)  and  accumulates  so  that 
it  can  be  breathed  while  the  beetle  swims  and  feeds  under 
water.  When  the  air  becomes  impure  the  beetle  rises  to 
the  surface,  forces  it  out,  and  accumulates  a  fresh  supply. 
The  beetles  are  very  voracious,  feeding  on  other  insects, 
and  even  on  small  fish.  The  eggs  are  laid  promiscuously  in 
the  water,  and  the  elongate  spindle-form  larvae  (fig.  77) 


FIG. 


74- — Army- worms,    larvae  of  the  moth,  Leucania  ^^n^pllncta,  on  corn. 
(Thotoeranh  by  M.  V.  Slingerland.) 


212 


ELEMENTARY  ZOOLOGY 


called  water-tigers  are  also  predaceous.      They  suck  the 
blood    from    other    insects    through    their    sharp-pointed 

sickle-shaped  hollow 
mandibles.  When  a  larva 
is  fully  grown  it  leaves 
the  water,  burrows  in 
the  ground,  and  makes  a 
round  cell  within  which  it 
undergoes  its  transforma- 
tions. The  pupa  state 
lasts  about  three  weeks 
in  summer,  but  the  larvae 
that  transform  in  autumn 
remain  in  the  pupa  state 
all  winter. 

The  June-beetles  (June- 
bugs)  (Lachnosterna  sp.) 
feed  on  the  foliage  of 
trees.  Their  eggs  are 
laid  among  the  roots  of 
grass  in  little  hollow  balls 
of  earth,  and  the  fat  slug- 
gish white  larvae  feed  on  the  grass-roots.  They  some- 
times occur  in  such  numbers  as  to  injure  seriously  lawns 
and  meadows.  The  larvae  live  three  years  (probably) 
before  pupating.  They  pupate  underground  in  an  earthen 
cell,  from  which  the  adult  beetle  crawls  out  and  flies  up 
to  the  tree-tops. 

Hymenoptera  :  the  ichneumon  flies,  ants,  wasps,  and 
bees. — TECHNICAL  NOTE. — Obtain  specimens  of  wasps,  both 
social  (distinguished  by  having  each  wing  folded  longitudinally)  and 
solitary  (wings  not  folded  longitudinally),  and  if  possible  of  both 
queens  (larger)  and  workers  (smaller)  of  the  social  kinds  ;  of  ants 
both  winged  (males  or  females)  and  wingless  (workers)  individ- 
uals ;  also  of  honey-bees,  including  a  queen,  drones,  and  workers, 
and  some  brood  comb  containing  eggs,  larvae,  and  pupae.  The  bee 


FIG.  75. — The  quince-curculio  (a  beetle), 
Conotracheliis  cratcegL  natural  size  and 
enlarged.  (Photograph  by  M.  V. 
Slingerland.) 


BRANCH  ARTHROPOD  A;   CLASS  IN  SECT  A :    THE  INSECTS  213 


specimens  can  be  got  of  a  bee  raiser.  Compare  the  external  struc- 
ture of  ants,  bees,  and  wasps  with  that  of  other  insects  ;  note  the 
pronounced  division  of  the  body  into  three  regions  (head,  thorax, 
abdomen)  ;  note  the  character  of  the  mouth-parts  having  mandibles 
fitted  for  biting  (ants  and  wasps)  or  moulding  wax  (honey-bees)  and 
having  the  other  parts  adapted  for  taking  both  solid  and  liquid 
food  ;  note  the  sting  (possessed  by  the  females  and  workers  only). 
Observe  the  behavior  of  bees  in  and  about  a  hive  ;  note  the  coming 
and  going  of  workers  for  food.  Observe  bees  collecting  pollen  at 
flowers  ;  observe  them  drinking  nectar.  Examine  the  honey-bee 


FIG.  76. — Immature  stages  of  the  quince  curculio,  Conotrachelus  crattzgi; 
at  the  left,  the  larva  natural  size  and  enlarged ;  at  the  right,  the  pupa. 
The  beetle  lays  its  eggs  in  pits  on  quinces,  and  the  larva  lives  inside 
the  quince  as  a  grub;  the  pupa  lives  in  the  ground.  (Photograph  by 
M.  V.  Sliugerland.) 

in  its  various  stages,  egg,  larva,  pupa,  adult.  Note  the  special 
structure  of  the  adult  worker  fitting  it  to  perform  its  various  special 
labors  ;  the  pollen-baskets  on  the  hind  legs  ;  the  wax-plates  on  the 
ventral  surface  of  the  abdomen,  the  wax-shears  between  tibia  and 
tarsus  of  hind  legs  ;  the  antennas-cleaners  on  the  fore  legs  ;  the 
hooks  on  front  margin  of  hind  wings,  etc. 

The  Hymenoptera  include  the  familiar  ants,  bees,  and 
wasps,  and  also  a  host  of  other  four- winged,  mostly 
small,  insects,  many  of  which  are  parasites  in  their  larval 
stage  on  other  insects.  All  Hymenoptera  have  a  com- 


2T4 


ELEMENTARY  ZOOLOGY 


plete  metamorphosis,  and  their  habits  and  instincts  are, 
as  a  rule,  very  highly  specialized.  The  parasitic  Hymen- 
optera  such  as  the  ichneumon  flies, 
chalcid  flies,  etc.,  are  stingless  but 
have  usually  a  piercing  ovipositor 
(the  sting  being  only  a  modified 
ovipositor).  The  general  life-history 
of  these  ichneumons  is  as  follows: 
the  female  ichneumon  fly,  finding 
one  of  the  caterpillars  or  fly  or  beetle 
larvae  which  is  its  host,  settles  on  it 
and  either  lays  an  egg  or  several 
eggs  on  it,  or  thrusting  in  its  ovi- 
positor, lays  the  eggs  in  the  body; 
the  young  ichneumon  hatching  as 
a  grub  burrows  into  the  body  of  its 
caterpillar  host,  feeding  on  the  body- 
tissues,  but  not  attacking  the  heart 
FIG.  77._Water-tiger,  the  or  nervous  system,  so  that  the  host 

larva  of  the  predaceous 


water-beetle,  Dyticus  sp. 
(From  specimen.) 


is  not  soon  killed ;    the  ichneumon 
pupates    either  inside    the  host,    or 

crawls  out  and,  spinning  a  little  silken  cocoon  (fig.   160), 

pupates    on  the   surface    of   the 

body  or  elsewhere. 

Some  of  the  stingless  Hymen- 

optera  are  not  parasites,  but  are 

gall-producers.    The  female  with 

its    piercing  ovipositor    lays    an 

egg  in  the  soft  tissue  of  a  leaf  or  FIG.  78.— The  plum  curcutio, 

stem,  and  after  the  larva  hatches       ConotraMus    nenuphar     a 

beetle  very  injurious  to  plums. 

the    gall    rapidly    forms.       The      (Photograph  by  M.  v.  Slin- 
larval  insect  lies  in    the    plant-      landt) 
tissue,  having  for  food  the  sap  which  comes  to  the  rapidly 
growing  gall.      It   pupates  in  the  gall,    and  when  adult 
eats  its  way  out. 


BRANCH  ARTHROPODS;   CLASS  INSECTA :    THE  INSECTS  215 

The  ants,  bees,  and  wasps  are  called  the  stinging 
Hymenoptera,  although  the  ants  we  have  in  North 
America  have  their  sting  so  reduced  as  to  be  no  longer 
usable.  Among  these  Hymenoptera  are  the  social  or 
communal  insects,  viz.,  all  the  ants,  the  bumblebees  and 
honey-bee,  and  the  few  social  wasps,  as  the  yellow-jacket 


FIG.  79. — The  currant-stem  girdler,  Janus  integer,  a  Hymenopteron  at 
work  girdling  a  stem  after  having  deposited  an  egg  in  the  stem  half  an 
inch  lower  down.  (Photograph  by  M.  V.  Slingerland.) 

and  black  hornet.  There  are  many  more  species  of  non- 
social  or  solitary  bees  and  wasps  than  social  ones,  and 
their  habits  and  instincts  are  nearly  as  remarkable. 

The  solitary  and  digger  wasps  do  not  live  in  com- 
munities as  the  hornets  do,  but  each  female  makes  a  nest 
or  several  nests  of  her  own,  lays  eggs  and  provides  for 


216  ELEMENTARY  ZOOLOGY 

her  own  young".  The  nest  is  usually  a  short  vertical  or 
inclined  burrow  in  the  ground,  with  the  bottom  enlarged 
to  form  a  cell  or  chamber.  In  this  chamber  a  single  egg 
is  laid,  and  some  insects  or  spiders,  captured  and  so  stung 
by  the  wasps  as  to  be  paralyzed  but  not  killed,  are  put  in 
for  food.  The  nest  is  then  closed  up  by  the  female, 
and  the  larva  hatching  from  the  egg  feeds  on  the  enclosed 
helpless  insects  until  full  grown,  when  it  pupates  in  the  cell 
and  the  issuing  adult  gnaws  and  pushes  its  way  out  of  the 
ground.  Each  species  of  wasp  has  habits  peculiar  to  itself, 
making  always  the  same  kind  of  nest,  and  providing 
always  the  same  kind  of  food.  Some  of  these  wasps  make 
their  nests  in  twigs  of  various  plants,  especially  those  with 
pithy  centres  in  the  stems.  For  interesting  accounts  of 
the  habits  of  several  digger  wasps  see  Peckham's  4<  The 
Solitary  Wasps." 

The  solitary  bees,  of  which  there  are  similarly  many 
kinds,  are  like  the  solitary  \vasps  in  general  habit,  only 
they  provision  the  nest  with  a  mixture  of  pollen  and  nectar 
got  from  flowers  instead  of  with  stung  insects.  Some- 
times many  individuals  of  a  single  species  of  solitary  bee 
will  make  their  nests  near  together  and  thus  form  a  sort 
of  community  in  which,  however,  each  member  has  its 
own  nest  and  rears  its  own  young.  In  the  case  of  certain 
small  mining  bees  of  the  genus  Halictus,  a  step  farther 
toward  true  communal  life  is  taken  by  the  common  build- 
ing and  use  by  several  females  of  a  single  vertical  tunnel 
or  burrow  from  which  each  female  makes  an  individual 
lateral  tunnel,  at  the  end  of  which  is  a  brood-chamber. 
Perhaps  half  a  dozen  females  will  thus  live  together,  each 
independent  except  for  the  common  use  of  the  vertical 
tunnel  and  exit. 

The  bumblebees  (J^ombus  sp.)  are  truly  communal  in 
habit.  All  the  eggs  are  laid  by  a  queen  or  fertile  female, 
which  is  the  only  member  of  the  colony  to  live  through 


BRANCH  ARTHROPODS;   CLASS  IN  SECT  A :    THE  INSECTS  2*7 

the  winter.  In  the  spring  she  finds  a  deserted  mouse's 
nest  or  other  hole  in  the  ground,  gathers  a  mass  of  pollen 
and  lays  some  eggs  on  it.  The  larvae,  hatching,  feed  on 
the  pollen,  dig  out  irregular  cells  for  themselves  in  it, 
pupate,  and  soon  issue  as  workers,  or  infertile  females. 
These  workers  gather  more  pollen,  the  queen  lays  more 
eggs,  and  several  successive  broods  of  workers  are  pro- 
duced. Finally  late  in  the  summer  a  brood  containing 
males  (drones)  and  fertile  females  (queens)  is  produced, 
mating  takes  place,  and  then  before  winter  all  the  workers 
and  drones  and  some  of  the  queens  die,  leaving  a  few 
fertilized  queens  to  hibernate  and  establish  new  communi- 
ties in  the  spring. 

The  yellow-jackets  and  hornets  (Vespidae),  the  so- 
called  social  wasps,  have  a  life-history  very  like  that  of 
the  bumblebees.  The  communities  of  the  social  wasps 
are  larger  and  their  nests  are  often  made  above  ground, 
being  composed  of  several  combs  one  above  the  other 
and  all  enclosed  in  a  many-layered  covering  sac  open 
only  by  a  small  hole  at  the  bottom.  This  kind  of  nest 
hangs  from  the  branch  of  a  tree  and  is  built  of  wasp-paper, 
which  is  a  pulp  made  from  bits  of  old  wood  chewed 
by  the  workers.  The  brood-cells  are  provisioned  with 
killed  and  chewed  insects,  the  larvae  of  both  solitary  and 
social  wasps  being  given  animal  food,  while  the  larvae 
of  both  solitary  and  social  bees  are  fed  flower-pollen  and 
honey.  As  in  the  bumblebees,  all  the  members  of  the 
community  except  a  few  fertilized  females  die  in  the 
autumn,  the  surviving  queens  founding  new  colonies  in 
the  spring.  The  queen  builds  a  miniature  "  hornet's 
nest  ' '  in  the  spring,  lays  an  egg  in  each  cell  and  stores 
the  cells  with  chewed  insects.  The  first  brood  is  com- 
posed of  workers,  which  enlarge  the  nest,  get  more  food, 
and  relieve  the  queen  of  all  labor  except  that  of  egg- 
laying.  More  broods  of  workers  follow  until  the  fall 


2l8 


ELEMENTARY  ZOOLOGY 


brood  of  males  and  females  appears,  after  which  the 
original  process  is  repeated. 

The  honey-bees  and  ants  show  a  highly  specialized 
communal  life,  with  a  well-marked  division  of  labor  and 
an  individual  sacrifice  of  independence  and  personal 
advantage  which  is  remarkable.  Their  communities  are 
large,  including  thousands  of  individuals,  and  the  struc- 
tural differences  among  the  males,  females,  and  workers 
are  readily  recognizable.  With  the  ants  the  workers  may 
be  of  two  or  more  sorts,  a  distinction  into  large  and  small 
workers  or  worker  majors  and  worker  minors  being  not 
uncommon. 

A  honey-bee  community,  living  in  hollow  tree  or  hive, 
includes  a  queen  or  fertile  female,  a  few  hundred  drones 
or  fertile  males,  and  ten  to  forty  thousand  workers,  in- 
fertile females  (fig.  80).  The  number  of  drones  and 


FIG.  80.  —The  honey-bee,  Apis  mellifica  ;  A,  queen,  B,  drone,  C,  worker. 
(From  specimens.) 

workers  varies,  being  smallest  in  winter.  Each  kind  of 
individual  has  a  certain  particular  part  of  the  work  of  the 
whole  community  to  do;  the  queen  lays  all  the  eggs,  that 
is,  is  the  mother  of  the  entire  community;  the  drones  act 
simply  as  the  royal  consorts,  fertilizing  the  eggs;  while 
the  workers  build  the  comb,  produce  the  wax  from 
which  the  cells  are  constructed,  bring  in  all  the  food  con- 


BRANCH  ARTHROPODA;   CLASS  INSECT  A :   THE  INSECTS  219 

sisting  of  flower-pollen  and  nectar,  care  for  the  young 
bees,  fight  off  intruders,  and  in  fact  perform  all  the  many 
labors  and  industries  of  the  community  except  those  of 
reproduction.  There  is  a  certain  not  very  well  understood 
and  perhaps  not  very  sharply  defined  division  of  these 
labors  among  the  worker  individuals,  the  younger  ones 
acting  specially  as  "  nurses,"  feeding  and  caring  for  the 
young  bees  (larvae  and  pupae),  the  older  ones  making  the 
food-gathering  expeditions.  The  queen  lays  her  eggs  one 
in  each  of  many  cells  (fig.  81).  These  eggs  hatch  in  three 
days,  and  the  young  bee  appears  as  a  white,  soft,  footless, 
helpless  grub  or  larva  that  is  fed  at  first  by  the  nurses  with 


FIG.  81. — Worker  brood  and  queen  cells  of  honey-bee  ;  beginning  at  the 
right  end  of  upper  row  of  cells  and  going  to  the  left  is  a  series  of  egg, 
young  larvae,  old  larvae,  pupa,  and  adult  ready  to  issue  ;  the  large 
curving  cells  below  are  queen  cells.  (From  Benton.) 

a  highly  nutritious  substance  called  bee-jelly  which  the 
nurses  make  in  their  stomachs  and  regurgitate  for  the 
larva.  After  two  or  three  days  of  this  feeding  the  larvae 
are  fed  pollen  and  honey.  After  a  few  days  a  small  mass 
of  this  food  is  put  into  the  cell,  which  is  then  "  capped  " 
or  covered  with  wax.  The  larva  after  using  up  this  food- 
supply  pupates,  and  lies  quiescent  in  the  pupal  stage  for 


220  ELEMENTARY  ZOOLOGY 

thirteen  days,  when  the,  fully  developed  bee  issues,  and 
breaking  through  the  wax  cap  of  the  cell  is  ready  for  the 
labors  which  are  immediately  assigned  it.  The  bee  with 
the  kind  of  life-history  just  described  is  a  worker.  It  has 
been  demonstrated  that  the  eggs  which  produce  workers 
and  those  which  produce  queens  do  not  differ,  but  if  the 
workers  desire  to  have  a  queen  produced  they  tear  down 
two  or  three  cells  around  some  one  cell,  enlarging  this 
latter  into  a  large  vase-shaped  cell.  When  the  larva 
hatches  from  the  egg  in  this  cell  it  is  fed  for  its  whole 
larval  life  with  bee-jelly.  From  the  pupa  into  which  this 
larva  transforms  issues  not  a  worker  but  a  new  queen. 
The  eggs  which  produce  drones  or  males  differ  from  those 
which  produce  queens  and  workers  in  being  unfertilized, 
the  queen  having  the  power  to  lay  either  fertilized  or 
unfertilized  eggs.  When  a  new  queen  appears  or  when 
several  appear  at  once  there  is  great  excitement  in  the 
community.  If  several  appear  they  fight  among  them- 
selves until  only  one  survives.  It  is  said  that  a  queen 
never  uses  its  sting  except  against  another  queen.  The 
old  queen  now  leaves  the  hive  accompanied  by  many  of 
the  workers.  She  and  her  followers  fly  away  together, 
finally  alighting  on  some  tree-branch  and  massing  there 
in  a  dense  swarm.  This  is  the  familiar  act  of  4<  swarm- 
ing."  Scouts  leave  the  swarm  to  find  a  new  home,  to 
which  they  finally  conduct  the  whole  swarm.  Thus  is 
founded  a  new  colony.  "This  swarming  of  the  honey- 
bee is  essential  to  the  continued  existence  of  the  species ; 
for  in  social  insects  it  is  as  necessary  that  the  colonies  be 
multiplied  as  it  is  that  there  should  be  a  reproduction  of 
individuals.  Otherwise  as  the  colonies  were  destroyed 
the  species  would  become  extinct.  With  the  social  wasps 
and  with  the  bumblebees  the  old  queen  and  the  young 
ones  remain  together  peacefully  in  the  nest;  but  at  the 
close  of  the  season  the  nest, is  abandoned  by  all  as  an 


BRANCH  ARTHROPOD  A;   CLASS  IN  SECT  A :    THE  INSECTS  221 

unfit  place  for  passing  the  winter,  and  in  the  following 
spring  each  young  queen  founds  a  new  colony.  Thus 
there  is  a  tendency  towards  a  great  multiplication  of 
colonies.  But  with  the  honey-bee  the  habit  of  storing 
food  for  winter,  and  the  nature  of  the  habitations  of  these 
insects,  render  it  possible  for  the  colonies  to  exist  in- 
definitely, and  thus  if  the  old  and  young  queens  remained 
together  peacefully  there  would  be  no  multiplication  of 
colonies  and  the  species  would  surely  die  out  in  time. 


FIG.  82.  —  Honey-bees  building  comb.     (From  Benton.) 

We  see,  therefore,  that  what  appears  to  be  merely 
jealousy  on  the  part  of  the  queen  honey-bee  is  an  instinct 
necessary  to  the  continuance  of  the  species." 

For  the  special  labors  of  gathering  food,  making  wax, 
building  cells,  etc.,  the  \vorkers  are  provided  wit'i  special 
structures,  as  the  pollen-baskets  on  the  outer  surface 
of  the  widened  tibia  of  the  hind  legs,  the  wax-shears 
between  the  tibia  and  first  tarsal  joint  of  the  hind  legs, 
the  wax-plates  on  the  ventral  surface  of  the  abdomen, 
etc.  A  great  many  interesting  things  connected  with  the 


222 


ELEMENTARY  ZOOLOGY 


life  and  industries  of  a  honey-bee  community  can  be 
learned  by  the  student  from  observation,  using  for  a  guide 
some  book  such  as  Cowan's  "Natural  History  of  the 
Honey-bee." 

The  gathering  of  food  from  long  distances,  the  details 
of  wax-making  and  comb-building,  of  honey-making  (for 


FIG.  83. — Comb  of  the  tiny  East  Indian  honey-bee,  Apis  jlorea,  one-third 
natural  size.      (From  Benton. ) 

the  nectar  of  flowers  is  made  into  honey  by  an  interesting 
process),  the  storing  of  food,  how  the  community  protects 
itself  from  starvation  when  winter  sets  in  or  food  is 
scarce  by  killing  the  useless  drones  and  the  immature 
bees  in  egg  and  larval  stage,  and  many  other  phenomena 
of  the  life  of  the  bee  community  present  good  opportuni- 
ties for  careful  observation  and  field  study.  Although 
the  community  is  a  persistent  or  continuous  one,  the  indi- 
viduals do  not  live  long,  the  workers  hatched  in  the 
spring  usually  not  more  than  two  or  three  months,  and 


BRANCH  ARTHROPODA;   CLASS  INSECTA :    THE  INSECTS  223 

those  hatched  in  the  fall  not  more  than  six  or  eight 
months.  But  new  ones  are  hatching  while  the  old  ones 
are  dying  and  the  community  as  a  whole  always  persists. 
A  queen  may  live  several  years,  perhaps  as  many  as  five. 
She  lays  about  one  million  eggs  a  year. 

There  are  more  than  two  thousand  known  species  of 
ants  (fig.  84),  all  of  which  live  in  communities  and  show  a 
truly  communal  life.  The  ant  workers  are  specially  dis- 
tinguished in  structure  from  the  males  and  females  by 
being  wingless,  and  in  numerous  species  there  are  two 
sizes  or  kinds  of  workers  known  as  \vorker  majors  and 
worker  minors.  The  life-history  and  communal  habits  of 
ants  are  not  so  thoroughly  known  as  are  those  of  the 
honey-bee,  but  they  show  even  more  remarkable  speciali- 
zations. The  ant  nest  or  formicary  is  with  most  species  an 
elaborate  system  of  underground  galleries  and  chambers, 
special  rooms  being  used  exclusively  for  certain  special 
purposes,  as  nurse-rooms,  food-storage  rooms,  etc.  The 
food  of  ants  comprises  many  animal  and  vegetable  sub- 
stances, but  the  favorite  food  with  many  species  is  the 
4 'honey-dew"  secreted  by  the  plant-lice  (Aphididae) 
and  scale  insects  (Coccidae).  To  obtain  this  food  an  ant 
strokes  one  of  the  aphids  with  its  antennae,  when  the  fluid 
is  excreted  by  the  insect  and  drunk  by  the  ant.  In  order 
to  have  a  certain  supply  oi  this  food  some  species  of  ants 
care  for  and  defend  these  defenseless  aphids,  which  have 
been  called  the  4<  cattle"  of  the  ants.  In  some  cases 
they  are  even  taken  into  the  ants'  nests  and  food  provided 
for  them.  "In  the  Mississippi  Valley  a  certain  kind  of 
plant-louse  lives  on  the  roots  of  corn.  Its  eggs  are 
deposited  in  the  ground  in  the  autumn  and  hatch  the  fol- 
lowing spring  before  the  corn  is  planted.  Now  the 
common  little  brown  ant  (Lasius  flaws]  lives  abundantly 
in  the  cornfields,  and  is  especially  fond  of  the  honey 
secreted  by  the  corn-root  louse.  So  when  the  plant-lice 


224 


ELEMENTARY  ZOOLOGY 


hatch  in  the  spring  before  there  are  corn-roots  for  them 
to  feed  on,  the  little  brown  ants  with  great  solicitude 
carefully  place  the  plant-lice  on  the  roots  of  a  certain 
kind  of  knot-weed  which  grows  in  the  field  and  protect 
them  until  the  corn  germinates.  Then  the  ants  remove 
the  plant-lice  to  the  roots  of  the  corn,  their  favorite  food- 


FIG.  84. — The  little  black  ant,  Monomorium  mimitum;  a,  female,  b,  female 
with  wings,  <r,  male,  </,  workers,  e,  pupa,  f.  larva,  g,  egg  of  worker, 
all  enlarged.  (From  Marlatt.) 

plant.      In  the  arid  lands  of  New  Mexico  and  Arizona  the 
ants  rear  scale  insects  on  the  roots  of  cactus. " 

The  ants  are  among  the  most  warlike  of  insects. 
Battles  between  communities  of  different  species  are 
numerous,  and  the  victorious  community  takes  possession 
of  the  food-stores  of  the  conquered.  Some  species  of  ants 
live  wholly  by  war  and  robbery.  In  the  case  of  the 


BRANCH  ARTHROPOD  A;    CLASS  INSECT  A :    THE  INSECTS  225 

remarkable  robber-ant  (Ecitori],  found  in  tropical  and  sub- 
tropical regions,  most  of  the  workers  are  soldiers,  and  no 
longer  do  any  work  but  fighting.  The  whole  community 
lives  exclusively  by  pillage.  Some  kinds  of  ants  go  even 
farther  than  mere  robbery  of  food-stores:  they  make 
slaves  of  the  conquered  ants.  There  are  numerous  species 
of  these  slave-making  ants.  They  attack  a  nest  of 
another  species  and  carry  into  their  own  nest  the  eggs 
and  larvae  and  pupae  of  the  conquered  community,  and 
when  these  come  to  maturity  they  act  as  slaves  of  the 
victors,  collecting  food,  building  additions  to  the  nest, 
and  caring  for  the  young  of  the  slave-makers. 

As  with  the  honey-bee  the  larval  ants  are  helpless 
grubs  and  are  cared  for  and  fed  by  nurses.  The  so-called 
44  ants'  eggs,"  the  little  white  oval  masses  which  we  often 
see  being  carried  in  the  mouths  of  ants  in  and  out  of  an 
ants'  nest,  are  not  eggs,  but  are  the  pupae  which  are 
being  brought  out  to  enjoy  the  warmth  and  light  of  the 
sun  or  being  taken  back  into  the  nest  afterward. 

There  are  in  this  country  numerous  species  of  ants 
showing  much  variety  of  habit  and  offering  excellent 
opportunities  for  most  interesting  field  observations.  For 
an  account  of  several  of  the  common  species  see  Corn- 
stock's  4<  Manual  of  Insects,"  pp.  633-643.  Ants  may 
be  readily  kept  in  the  schoolroom  in  an  artificial  nest  or 
formicary  and  their  life-history  and  habits  closely  watched. 
For  full  directions  for  making  and  keeping  a  simple  and 
inexpensive  formicary  see  Comstock's  44  Insect  Life," 
pp.  278-281.  For  an  interesting  account  of  some  of  the 
habits  of  the  social  insects  see  Lubbock's  "Ants,  Bees, 
and  Wasps. ' ' 


226 


ELEMENTARY  ZOOLOGY 


CLASS  MYRIAPODA  :   THE  MYRIAPODS,  OR  CENTIPEDS 

AND    MlLLIPEDS. 

Belonging  to  the  branch  Arthropoda,  with  the  classes 
Crustacea  and  Insecta,  are  three  other  classes,  of  which 
one,  the  Onychophora,  is  represented  by  a  single  genus 
Peripatus  (Fig.  85),  of  extremely  interesting  animals. 
However,  as  these  animals  are  not  found 
in  the  United  States  we  cannot  study 
them.  The  other  two  classes  are  the 
Myriapoda,  including  the  centipeds  and 
millipeds  or  thousand-legged  worms,  and 
the  Arachnida,  including  the  scorpions, 
spiders,  mites,  and  ticks.  All  these 
animals  are  often  spoken  of  as  insects, 
but  though  related  to  them  they  are  not 
true  insects. 

TECHNICAL  NOTE. — From  under  stones  or 
logs  obtain  specimens  of  millipeds,  or  thousand- 
legged  worms  (large  blackish,  cylindrical,  worm- 
like  animals  with  each  body-segment  back  of  the 
fourth  bearing  two  pairs  of  jointed  legs)  ;  also 
specimens  of  centipeds  or  hundred-legged  worms 
(flattened,  usually  brownish  or  pale  worm-like 
animals  with  the  body-segments  bearing  only  one 
pair  of  legs  each)  in  the  same  places.  Examine 
the  external  structure  ;  note  number  of  body- 
rings  ;  division  into  body-regions  ;  presence  of 
FIG.  85. — Peripatus  antennae;  character  and  number  of  eyes;  charac- 
eiseni  (Mexico),  ter  of  mouth-parts  ;  character  and  arrangement 
(From  specimen.)  of  jegS>  jn  tne  centipeds  the  first  pair  of  legs  is 
modified  to  form  a  pair  of  poison-fangs.  They  appear  to  belong  to 
the  mouth-parts.  The  internal  anatomy  will  be  found  to  be,  if 
examined,  much  like  that  of  insects  and  can  be  studied  from  the 
account  of  the  anatomy  of  the  water-scavenger  beetle  and  butterfly 
larva.  Compare  the  Myriapods  with  the  Hexapods  or  true  insects. 
What  are  the  points  of  resemblance  ?  what  are  the  points  of  differ- 
ence ? 

The  Myriapoda  are  land-animals  breathing  by  means 
of  tracheae  like  the  insects.      In  them  the  body-segments 


BRANCH  AR  THRU  POD  A  ;  CLASS  M  YRIAPODA :  M  YRIAPODS  227 


are  nearly  uniform  in  character  with  the  exception  of  the 

head,  which,  as  in  the  insects,  bears  the  mouth-parts  and 

antennae.      There  is  no  grouping  of  the  body-segments 

into  regions  except  as  the  head  is  opposed  to  the  rest  of 

the  body.      (In  a  few  myriapods  there  are  indications  of 

a  division  of  the  hind  body  into  thorax  and  abdomen.) 

The   presence   of  true   legs   on    all    the 

segments   of  the    hinder    region   of  the 

body  and  the  lack  of  the    three-region 

division  of  the  body    are  the    principal 

external  structural  characteristics  which 

distinguish  myriapods  from  insects.    The 

internal  anatomy  corresponds  in  general 

character  with  that  of  insects. 

The   most  familiar  myriapods  are  the 

millipeds,  and  the  lithobians  and  centi- 

peds.      The  millipeds  are  cylindrical  in 

shape,   have  two  pairs  of  legs  on  most 

of  the  body-segments  and  are  vegetable 

feeders,  though  some  may  feed  on  dead 

animal     matter.         The     galley-worms 

{Julus)  (fig.  86),  large,   blackish,  cylin- 
drical millipeds  found  under  stones  and 

logs   and  leaves  and    in  loose  soil,   are 

familiar  forms.      They  crawl  slowly  and  when  disturbed 

curl  up  and  emit  a  malodorous  fluid.  They  can  easily  be 
kept  alive  in  shallow  glass  vessels  with  a  layer  of  earth  in 
the  bottom,  and  their  habits  and  life-history  may  thus  be 
studied.  They  should  be  fed  sliced  apples,  green  leaves, 
grass,  strawberries,  fresh  ears  of  corn,  etc.  They  are  not 
poisonous  and  may  be  handled  with  impunity.  They  lay 
their  eggs  in  little  spherical  cells  or  nests  in  the  ground. 
An  English  species  of  which  the  life-history  has  been 
studied  lays  from  60  to  100  eggs  at  a  time.  The  eggs 
of  this  species  hatch  in  about  twelve  days. 


FIG.  86.— A  galley- 
worm  (milliped), 
Julits  sp.  (From 
specimen.) 


228 


ELEMENTARY  ZOOLOGY 


The  lithobians  and  centipeds  are  flattened  and  have 
but  a  single  pair  of  legs  on  each  body-ring.  They  are 
predaceous  in  habit,  catching  and  killing  insects,  snails, 

earthworms,  etc.  They  can 
run  rapidly,  and  have  the  first 
pair  of  legs  modified  into  a 
pair  of  poison-claws,  which 
are  bent  forward  so  as  to  lie 
near  the  mouth.  The  com- 


FIG.  87.— The  skein  centi- 
ped,  Scutigera  forceps,  nat- 
ural size,  common  in  houses 
and  conservatories.  (From 
Marlatt.) 


FIG.  88.—  Acentiped,  Scolo- 
pendra  sp.  (From  speci- 
men.) 


mon  ''skein"  centiped  (Scutigera  forceps]  (fig.  87)  is 
yellowish  and  has  fifteen  pairs  of  legs,  long  4O-segmented 
antennae,  and  nine  large  and  six  smaller  dorsal  segmental 


BRANCH  ARTHROPODA ;  CLASS  ARACHNID  A :  SPIDERS  229 

plates.  The  true  centipeds  (Scolopcndra)  (fig.  88)  have 
twenty-one  to  twenty-three  body-rings,  each  with  a  pair 
of  legs,  and  the  antennae  have  seventeen  to  twenty  joints. 
They  live  in  warm  regions,  some  growing  to  be  very 
large,  as  long  as  twelve  inches  or  more.  The  "  bite  "  or 
wound  made  by  the  poison-claws  is  fatal  to  insects  and 
other  small  animals,  their  prey,  and  painful  or  even 
dangerous  to  man.  The  popular  notion  that  a  centiped 
"  stings  "  with  all  of  its  feet  is  fallacious.  It  is  recorded 
by  Humboldt  that  centipeds  are  eaten  by  some  of  the 
South  American  Indians. 


CLASS  ARACHNIDA:  THE  SCORPIONS,  SPIDERS,  MITES, 
AND  TICKS. 

TECHNICAL  NOTE. — Obtain  specimens  of  various  spiders ;  the 
running  or  hunting  spiders  may  be  found  on  the  ground,  especially 
under  stones  and  boards,  the  web-makers  on  their  snares.  Get 
also  spiders'  "  cocoons  "  (egg-sacs).  Examine  the  external  structure 
of  the  spider  ;  note  the  two  body-regions  ;  the  number  and  character 
of  legs  ;  the  absence  of  antennas  ;  the  number  and  arrangement  of 
the  eyes  (which  are  simple,  not  compound)  ;  the  mouth-parts,  espe- 
cially the  large  mandibles  ;  the  spinnerets  at  the  tip  of  the  abdomen 
(examine  a  cut  off  spinneret  under  the  microscope  to  see  the  spin- 
ning-tubes) ;  note  the  breathing  openings  or  spiracles  on  under  side 
of  abdomen.  Obtain  also  a  scorpion  if  possible,  and  some  ticks  and 
mites.  Compare  with  the  spiders  and  note  that  in  the  scorpion 
the  body  is  plainly  seen  (especially  in  the  abdomen)  to  be  composed 
of  segments.  Note  the  extreme  fusion  of  the  segments  and  body- 
regions  in  the  mites  and  ticks.  The  common  red  spider  of  hot- 
houses and  gardens  is  a  mite  ;  ticks  may  sometimes  be  found  on 
dogs.  Observe  various  kinds  of  spider-webs,  and  try  to  observe 
the  process  of  web-making  (this  can  be  observed  early  in  the  morn- 
ing or  about  dusk)  by  one  of  the  orb-weaving  garden-spiders. 
Live  spiders  can  be  kept  in  the  schoolroom  and  their  feeding 
habits  and  perhaps  web-making  habits  observed. 

The  class  Arachnida  is  composed  of  Arthropods  whose 
body-segments  are  grouped  into  two  regions,  a  cephalo- 
thorax  bearing  the  mouth-parts,  eyes,  and  legs,  and  an 
abdomen.  The  segments  composing  these  two  parts  are 


210 


ELEMENTARY  ZOOLOGY 


so  fused  that,  except  in  the  scorpions,  they  are  usually 
indistinguishable.  There  are  no 
antennae,  the  eyes  are  simple,  the 
mouth-parts  fitted  for  biting,  and 
there  are  four  pairs  of  legs.  In 
their  internal  anatomy  the  arach- 
nids show  in  some  forms  a  pecu- 
liar modification  of  the  respiratory 
organs,  the  tracheae  being  flat  and 
leaf-like  and  massed  together  in  a 
few  groups  rather  than  being  tubular 
and  ramifying  through  the  body. 

The  dorsal  vessel  or  heart  usu- 
ally has  a  few  blood-vessels  or 
arteries  running  from  it.  This  class 
is  divided  into  three  orders,  the 

FIG.  89.— A  scorpion  Cen-  Arthrogastra,     or     scorpions,      the 

trurus    sp.,    from    Cali-     A  r~r:nQ 
fornia.  (From  specimen.)    1  ld> 

o  r    mites 

and  ticks,  and  the  Araneina,  or 
spiders. 

The  scorpions  (fig.  89)  have 
the  posterior  six  segments  of 
the  abdomen  much  narrower 
than  the  seven  anterior  seg- 
ments and  forming  a  tail  which 
bears  at  its  tip  a  poison-fang  or 
sting.  This  sting  is  used  to  kill 
prey,  insects  and  other  small 
animals.  The  tail  can  be  darted 
forwards  over  the  body  to  strike 
prey  which  has  been  previously  FlG. 
seized  by  the  large  pincer-like 
maxillary  palpi.  Scorpions  are 
common  in  warm  regions,  about  twenty  species  being 


cheese-mite,  Ty- 
roglyphus  siro,  greatly  en- 
larged. (After  rk-rlese.) 


BRANCH  ARTHROPODS ,   CLASS  ARACHNID  A :  SPIDERS   231 

known  in  southern  North  America.  Their  sting  though 
painful  is  not  dangerous  to  man.  The  young  are  born 
alive  and  are  carried  about  by  the  mother  for  some  time 
after  birth. 

The  mites  (figs.  90  and  91)  and  ticks  (fig.  92)  are 
mostly  small  obscure  animals,  which  live  more  or  less 
parasitically.  The  common  red  spider  of  house-plants 
as  well  as  the  sugar-  and  cheese-mites,  the  dreaded 


FIG.  91. — Bird  mite,  species  undetermined,  from  the  gnome-owl,  Glauci- 
dium  gnomus.     (Photo-micrograph  by  Geo.  O.  Mitchell.) 

itch-mite  and  the  chigger  are  familiar  examples  of  these 
degraded  arachnids,  and  the  wood-ticks,  dog-  and 
chicken-ticks  are  common  examples  of  the  larger  blood- 
sucking forms.  The  body  in  both  mites  and  ticks  is  very 
compact,  the  two  body-regions,  cephalothorax  and  ab- 
domen, being  closely  fused. 

The  spiders  have  the  abdomen  distinctly  set  off  from  the 
cephalothorax.  The  eyes  (fig.  93)  vary  in  number  and 
arrangement,  the  mandibles  are  large,  each  being  com- 
posed of  two  parts,  a  basal  hair-covered  part,  the  falx,  and 
a  terminal  smooth,  shining,  slender,  sharp-pointed  part, 


ELEMENTARY  ZOOLOGY 


the  fang,    which    is    movably    articulated    with    the    falx 
(fig.  93  \      In  the  falx  is  a  poison-sac  from  which  poison 


FIG.  92. — The  dog  or  wood  tick,  Dermacentor  americanus  male,  the  most 
common  tick  in  the  Northern  States.     (After  Osborn.) 

flows  through  the  hollow  fang  and  out  at   its  tip.      The 
legs  vary  in  relative  length  in  different  spiders,  and  each 
is   made  up  of  seven  joints.      The  spinnerets 
(fig.  94),  which  are  situated  at  the  tip  of  the 
abdomen,  are  six  in  number  (a  few  spiders 
have    only   four),   and    are    like    little  short 
fingers.      They  have  at  their  tips  many  fine 
FIG.  93.—  The   little  spinning-tubes  from  each   of  which    a 
showh" d  ^fafx   ^ne  S1*^en  thread  issues  when  the  spider  is 
and  fang  of  a   spinning.      These  many  fine  threads  fuse  as 
Jenkins  ^  a™™   ^^  issue  to  form  a  single  strong  cable  or 
Kellogg.)          sometimes    a  flat  rather   broad  band.      The 
spinnerets  are  movable,    and  by  their  manipulation    the 
desired  kind  of  line  is  produced.      The  silk  comes  from 


BRANCH  ARTHROPODS  ;  CLASS  ARACHNID  A  :  SPIDERS  233 


many  silk-glands  in  the  abdomen,  from  each  of  which  a 
fine  duct  runs  to  a  spinning-tube. 

The  spiders  may  be  divided  into  two  groups  according 
to    their  habits,   viz.,  the   wandering  or  hunting  spiders, 


FIG.  94. — The  six  spinner- 
ets (below)  of  a  spider, 
with  one  spinneret  en- 
larged (above)  to  show 
the  spinning  "spools" 
or  tubes.  (From  Jenkins 
and  Kellogg.) 


FIG.  95. — A  long-legged  spider, 
Tetragnatha  sp.,  on  its  web. 
(From  life.) 


which  do  not  spin  webs  to  catch  their  prey,  and  the 
sedentary  or  web- weaving  spiders,  which  spin  snares  to 
catch  their  prey.  The  wandering  spiders  can  spin  silk, 
however,  and  often  do  so  to  line  their  burrows,  to  make 
nests,  or  to  make  egg-sacs. 

The   hairy  tarantulas     and    the    trap-door    spiders    of 
similar  appearance    are   among    the  most   interesting  of 


234 


ELEMENTARY  ZOOLOGY 


the  hunting  spiders.  They  live  in  vertical  burrows  or 
tunnels  in  the  ground  which  are  lined  with  silk,  and  which 
in  the  case  of  the  trap-door  spider  are  covered  with  a  door 
or  lid  made  of  silk  and  soil.  The  top  of  this  door  is 


FIG.  96. — A  running  spider  (Ly.osidse;.     (From  life.) 

always  covered  with  soil  or  bits  of  leaves  or  twigs  so  that 
it  is  nearly  indistinguishable  from  the  surface  of  the 
ground  about  it.  When  the  nest  is  in  ground  covered 
with  moss  the  spider  covers  the  door  with  moss.  The 


FIG.  97.  — A  female  running  spider  (Lycosidse)  carrying  its  egg-sac  about 
attached  to  its  spinnerets.      (From  Jenkins  and  Kellogg. ) 


tarantulas  hunt  at  night  and  rest  in  the  burrow  in  the 
daytime.  They  are  very  large,  sometimes  having  an 
expanse  of  legs  of  6  inches. 

The   common,  rather   large   swift  black   spiders   found 


BRANCH  ARTHROPOD  A  ;  CLASS  ARACHNID  A :  SPIDERS   235 

under  stones  and  boards  are  hunting  spiders,  belonging 
to  the  family  Lycosidae  and  are  called  the  running  spiders 
(fig.  96).  They  -live  in  burrows  in  the  ground,  coming 
out  to  stalk  and  chase  their  prey.  The  eggs  are  laid  in 
globular  egg-sacs  which  are  often  carried  about,  attached 
to  the  spinnerets,  by  the  female  (fig.  97).  The  young 
spiderlings  after  hatching,  in  some  species,  climb  on  to 
the  mother's  back  and  are  carried  by  her  for  some  time. 
Other  kinds  of  wandering  or  hunting  spiders  are  the  crab- 
spiders  (Thomisidae)  (fig.  98),  which  run  sidewise  or  back- 
ward as  well  as  forward,  and  the  black  and  red,  fierce- 


FIG.  98.  —  A   crab-spider   (Thomi-     FIG.   99. — A  jumping  spider  (Atti- 
sidae).  (From  Jenkins  and  Kellogg.)         dae.)   (From  Jenkins  and  Kellogg.) 

eyed,  stout-bodied  little  jumping  spiders  (Attidae)  (fig.  99), 
which  leap  on  their  prey. 

The  sedentary  or  web-weaving  spiders  are  of  various 
kinds.  They  may  be  grouped  according  to  their  spinning 
habits  into  cobweb  weavers  (Therididae),  small  slim- 
legged  spiders  which  make  the  familiar  unsymmetrical 
cobwebs  of  houses  and  outbuildings ;  funnel-web  weavers 
(Agalenidae),  larger  long-legged  spiders  of  meadow  and 
field  which  spin  a  flat  or  concave  horizontal  web  in  the 
grass  with  a  silken  tube  leading  down  to  the  ground; 
the  curled-thread  weavers  (Dictynidae),  which  use  in  addi- 
tion to  the  usual  lines  peculiar  broad  lines  made  of  waved 
or  curled  threads  in  their  irregular  webs  made  in  fence- 


236  ELEMENTARY  ZOOLOGY 

corners  and  on  plants ;  and  finally  orb-weavers  (Epeiridae) 
(fig.  100),  the  host  of  variously  colored  and  patterned 
stout-bodied  garden-spiders  which  spin  the  beautiful  sym- 
metrical circular  webs  familiar  to  all  (fig.  101).  If  a 
complete  uninjured  orb  web  be  examined  it  will  be  found 
to  consist  of  a  small  central  hub  either  open  or  closed, 
from  which  run  radii  to  the  outer  edges  of  the  web. 
Around  the  hub  is  an  open  or  free  zone,  and  farther  out 
a  spiral  zone,  so  called  because  a  line  running  in  close 


FIG.    100. — Argiope  sp.,   a  large  orb- weaver  (Epeiridse).     (From   Jenkins 
and  Kellogg.) 


spiral  turns  fills  in  the  space  between  the  radii.  This  is 
the  real  prey-catching  part  of  the  snare,  and  the  silken 
line  here  is  sticky,  while  the  radii  and  some  other  parts 
of  the  web  are  made  of  silk  that  is  not  sticky.  The 
web  is  supported  by  strong  foundation-lines,  attached  to 
leaves,  stems,  or  whatever  is  firm  in  the  neighborhood  of 
the  web.  The  spider  either  rests  on  the  web,  usually  in 
the  centre,  or  lies  concealed  in  a  nest  or  tent  near  at  hand 
from  which  a  special  path-line  runs  to  the  centre  of  the 
web.  The  building  of  one  of  these  orb  webs  is  a  great 


BRANCH  ARTHROPOD/.  ;  CLASS  ARACHNID  A :  SPIDERS  237 

work,  and  is  done  with  extraordinary  nicety  of  manipula- 
tion by  the  use  of  feet  and  spinnerets.     For  account  of 


FIG.  ioi.— Spider  and  its  web  in  a  rose-bush.  (Photograph  from  life  by 
Cherrv  Kearton;  from  "Wild  Life  at  Home,"  by  permission  of  Cassell 
&Co.). 

web-making,  etc.,  see  McCook's  "American  Spiders  and 
their  Spinning  Work." 

The  habits  and  instincts  of  spiders  in  connection  with 
the  care  of  the  young,  the  building  of  webs  and  nests, 
ballooning  by  means  of  silken  lines,  the  active  stalking 
and  catching  of  prey,  etc.,  are  very  interesting  and  offer 


238 


ELEMENTARY  ZOOLOGY 


a  good  field  for  independent  observation  and  study  by  the 
student. 


FPG.  102. — The  triangle  spider,  Hyptiotes  sp.  (California),  with  its  web;  the 
spider  rests  on  the  taut  guy-line,  with  a  loop  of  the  line  held  between 
its  fore  and  hind  legs;  when  an  insect  gets  into  the  web  the  spider 
loosens  the  hold  of  its  hind  feet  on  the  guy-line,  thus  allowing  the  web 
to  spring  forward  sharply  and  further  entangle  the  prey.  (From 
Jenkins  and  Kellogg.) 


CHAPTER   XXII 
MOLLUSCA:  THE    MOLLUSCS 

THE   FRESH-WATER   MUSSEL 


Structure  (fig.  103).  —  TECHNICAL  NOTE.  —  The  fresh-water  01 
river  mussel  lives  commonly  in  the  streams  and  lakes  or  ponds  in 
the  United  States.  It  frequents  muddy  or  sandy  bottoms.  Speci- 
mens can  often  be  secured  with  a  long-handled  rake  from  the  shore 
or  picked  up  in  shallow  streams  with  the  hand.  If  possible  to  keep 
the  animals  alive  until  ready  for  use,  some  of  their  habits  may  be 
observed.  Place  them  in  a  tub  or  trough  with  water  and  mud  ; 
when  they  have  settled  themselves  put  some  powdered  carmine, 
starch,  or  similar  substance  in  the  water  near  them,  and  note  the 
water-currents. 

Living  mussels  which  have  been  placed  in  a  dish  with 
mud  several  inches  deep  and  covered  with  water  will  be 
seen  to  travel  in  a  definite  direction.  The  end  which  is 
in  front  is  the  head  end.  Note  the  process  of  thrusting 
out  and  retracting  the  fleshy/^/  which  extends  between 
the  two  valves  of  the  shell.  Note  that  the  two  valves  are 
held  together  along  the  upper,  or  dorsal,  surface  by  a 
horny  structure,  the  hinge  -ligament.  Note  near  the  hinge- 
line  a  prominence  (umbo)  in  each  valve  from  which  ex- 
tends a  series  of  concentric  lines  of  growth.  The  umbo 
is  the  oldest  part  of  the  valve.  Note  at  the  lower  edge 
of  the  valves  a  soft  membrane  with  a  fringe  along  its  free 
border.  This  is  the  edge  of  the  mantle-lobes,  flaps  of  the 
body-wall  which  cover  the  body  and  which  aid  in  the 
functions  of  respiration  and  nutrition. 

239 


240  ELEMENTARY  ZOOLOGY 

TECHNICAL  NOTE. — Specimens  which  are  to  be  dissected  should 
be  killed  by  dropping  them  for  a  few  seconds  into  warm  water,  when 
the  muscles  will  relax  enough  so  that  a  chip  may  be  thrust  between 
the  valves.  If  specimens  are  to  be  kept  for  some  time  before  dis- 
secting they  should  be  preserved  in  alcohol  or  4^  formalin.  In  a 
dead  specimen  carefully  remove  the  left  valve.  This  is  accomplished 
by  slipping  in  a  thin  knife-blade  close  to  the  inner  edge  of  the  left 
valve  and  carefully  cutting  the  two  large  adductor  muscles  which 
bind  the  valves  together.  The  dissection  should  be  made  under 
water. 

Before  the  removal  of  the  valve,  as  just  described, 
notice  a  portion  of  the  mantle  adhering  to  the  Inner  face 
of  the  valve,  along  a  line  of  attachment  indicated  by  a 
crease.  This  is  the  pallial  line.  After  the  left  valve  has 
been  removed,  the  mantle  being  carefully  separated  from 
it,  note  the  large  conical  projections  from  the  valves,  the 
hinge  teeth,  which  fit  into  each  other.  Note  the  large 
muscle  impression  just  in  front  of  the  hinge-teeth ;  this  is 
the  point  of  attachment  of  the  anterior  addtictor  muscle, 
while  just  behind  and  adjoining  it  is  the  impression  of  the 
anterior  retractor  muscle.  Note  posterior  to  the  adductor 
and  below  the  retractor  a  small  impression  which  affords 
attachment  for  the  protractor  muscles  of  the  foot.  At 
the  other  end  of  the  valve,  note  the  large  impression  of  the 
posterior  adductor  muscle  with  the  impression  of  the  small 
posterior  retractor  muscle  just  above  it. 

TECHNICAL  NOTE. — Lift  back  the  left  mantle-lobe,  thus  exposing 
the  body  parts  underneath. 

Note  the  projecting  muscular  foot,  the  movements  of 
which  are  governed  by  the  retractor  and  protractor 
muscles  attached  to  the  impressions  just  mentioned. 
Note  a  pair  of  flattened  plate-like  structures  composed  of 
thin,  ribbed,  membranous  folds.  These  are  the  gills. 
Note  just  beneath  the  anterior  adductor  muscle  a  small 
opening  leading  into  the  soft  visceral  mass  of  the  body. 
This  is  the  mouth.  Note  near  the  mouth  two  pairs  of 
olate-like  structures  much  smaller  than  the  gills.  These 


MOLLUSC/1:   THE  MOLLUSCS  253 

second  or  hinder  pair),  and  the  respiratory  pore.     Note  the  streak 
of  mucus  left  by  the  slugs  in  crawling  about. 

Some  sea-shells  can  be  got  from  private  collections  of  "  curios" 
to  illustrate  the  variety  of  form  of  the  univalve  shells. 

Perhaps  one-half  of  all  the  known  species  of  molluscs 
are  snails  and  slugs  (fig.  108).  Snails  are  either  aquatic  or 
terrestrial  in  habit,  but  in  either  case  they  (the  true  pulmo- 
nate  snails)  breathe  not  by  means  of  gills,  as  do  most  of 
the  other  molluscs,  but  by  means  of  a  so-called  "  lung." 
This  lung  is  a  sac  with  an  external  opening  on  the  right 
side  of  the  body  and  with  its  inner  sutjace  richly  furnished 
with  fine  blood-vessels.  The  exchange  of  gases  between 
the  blood  and  the  outer  air  takes  place  through  the  thin 
walls  of  the  blood-vessels.  Most  snails  which  live  in  the 
water,  as  the  pond-snails  and  the  river-snails,  have  to 
come  occasionally  to  the  surface  to  breathe.  These  fresh- 
water and  land-molluscs  which  possess  a  lung-sac  instead 
of  gills  constitute  the  order  Pulmonata.  The  pulmonate 
pond-  and  land-snails  and  slugs  are  vegetable  feeders  and 
where  they  occur  in  large  numbers  do  much  injury  to 
vegetation.  While  the  common  pond-snails  have  but 
one  pair  of  feelers,  at  the  base  of  which  are  found  the 
eyes,  most  of  the  land-snails  and  slugs  have  two  pairs  of 
'  *  horns, ' '  the  eyes  being  on  the  tips  of  the  second  pair. 
The  lung-sac,  besides  serving  as  a  breathing  organ,  also 
enables  the  snail  to  rise  or  sink  according  as  the  animal 
varies  the  size  of  the  sac  and  consequently  the  amount  of 
air  in  it.  All  the  Pulmonata  are  hermaphroditic,  each 
individual  producing  both  sperm-  and  egg-cells.  The 
eggs  of  the  pond-snail  "  are  laid  in  gelatinous  transparent 
capsules,  half  an  inch  to  an  inch  in  length,  flattened  and 
linear  or  oblong  in  outline.  After  a  few  snails  have  been 
kept  a  short  time  in  a  small  vessel  of  water  with  their 
appropriate  food,  these  egg-capsules  may  be  looked  for 
on  the  bottom  and  sides  of  the  vessel  or  closely  adherent 


254  ELEMENTARY  ZOOLOGY 

to  the  stems  or  leaves  of  plants  placed  in  the  water. 
They  are  so  transparent  as  to  be  easily  overlooked." 
Young  snails  may  be  reared  from  these  eggs. 

There  are  other  snails  common  in  ponds,  also  called, 
like  the  pulmonate  forms,  pond-snails,  which  have  gills 
and  no  lung-sac.  These  pond-snails  belong  to  a  different 
order  of  molluscs,  and  live  on  the  bottom  of  the  pond, 
crawling  about  in  the  soft  mud  and  feeding  on  animal 
instead  of  vegetable  food. 

The  shells  of  the  various  kinds  of  snails  vary  much. 
In  many  of  the  land-snails  the  spiral  is  not  spire-shaped 
or  conical,  but  is  flat.  In  some  the  whorls  of  the  spiral 
run  from  left  to  right  (dextral)  when  the  shell  is  looked 
at  with  apex  held  toward  one,  while  in  others  the  whorls 
run  from  right  to  left  (sinistral). 

Of  the  hosts  of  marine  Gastropods  we  can  notice  only 
a  few  kinds.  The  nudibranchs  (fig.  109)  are  a  group  of 


FlG.  109. — Three  Pacific  Coast  nudibranchs;  Doris  tuberculata  (in  lower 
left-hand  corner),  Echinodoris  sp.  (upper  one),  and  Triopha  modes ta 
(at  right).  (From  living  specimens  in  a  tide-pool  on  the  Bay  of  Mon- 
terey, California.) 

beautiful  forms  in  which  the  shell  is  wholly  wanting  and  f 
the  mantle  is  usually  absent.     The  gills  are  thus  exposed 
and  are  usually  in  the  shape  of  delicate  freely  projecting 


V 

MOLLUSCS:   THE  MOLLUSCS  241 

are  the  labial  palpi,  and  it  is  by  their  action  that  food- 
particles  which  have  been  brought  in  with  the  water  are 
conveyed  to  the  mouth.  Note  at  the  posterior  part  of 
each  mantle-lobe  a  fringed  portion  which,  together  with 
a  corresponding  part  on  the  other  side,  forms  the  inhalant 
sipJion.  The  cilia  of  the  fringes  carry  water  and  food- 
particles  into  the  space  enclosed  by  the  mantle- lobes; 
this  space  is  the  mantle-cavity.  After  the  food  has  been 
taken  o^it  and  the  water  has  passed  through  the  finely 
striated  gills  it  is  collected  in  a  common  cavity  which 
extends  above  the  two  sets  of  gills  on  each  side.  This 
space  is  called  the  supra-branchial  cavity.  This  cavity 
is  continuous  posteriorly  with  a  space  between  the  right 
and  left  mantle-lobes,  which  is  connected  with  the 
exterior  by  an  opening  above  the  inhalant  siphon  called 
the  exlialant  sip/ion.  The  function  of  the  gills  is  partly 
to  produce  currents  of  water  carrying  the  food  to  the 
mouth,  and  partly  respiratory^  The  mantle  is  an  impor- 
tant organ  of  respiration.  / 

Make  a  drawing  showing  the  organs  described ^TT^ 

TECHNICAL  NOTE. — Carefully  cut  away  the  mantle  and  gills 
from  the  leftside,  and  also  the  labial  palpi,  being  careful  not  to  dis- 
turb the  visceral  mass. 

Note  two  openings  along  the  line  where  the  gills  and 
foot  come  together.  The  uppermost  is  the  opening  of  the 
ureter  giving  exit  to  the  excretion  from  the  kidneys;  the 
lower  is  the  opening  of  the  duct  frofn  the  reproductive 
organs  and  is  called  the  genital  aperture.  The  products 
from  both  of  these  organs  are  carried  out  through  the 
exhalant  siphon^ 

Note  that  th*  mouth  leads  by  a  short  tube  (oesophagus 
or  gullet)  into  a  large  cavity,  the  stomach,  which  is  sur- 
rounded by  a  greenish  mass,  the  digestive  gland. 

TECHNICAL  NOTE. — Carefully  cut  the  delicate  covering  of  the 
dorsal  portion  of  the  visceral  mass  and  expose  a  cavity. 


242  ELEMENTARY  ZOOLOGY 

The  cavity  thus  exposed  is  the  pericardium.  Note 
within  the  pericardium  a  long  tube  extending  through  it. 
This  is  a  portion  of  the  alimentary  canal,  the  rectum, 
which  opens  posteriorly  through  the  anus  into  the  supra- 
branchial  chamber.  Note  a  muscular  sac  about  the 
rectum  midway  of  its  course  through  the  pericardium. 
This  is  the  unpaired  ventricle  of  the  heart.  Attached  to 
each  side  of  the  ventricle  are  thin-walled  sacs,  the  right 
and  left  auricles,  which  are  entered  by  fine  blood-vessels, 
the  efferent  branchial  veins,  from  the  right  and  left  gills. 
The  blood  brought  through  these  blood-vessels  from  the 
gills  flows  into  the  auricles  and  from  them  into  the  un- 
paired muscular  ventricle,  from  which  it  is  forced  anteriorly 
and  posteriorly  through  two  main  arteries,  the  anterior 
and  posterior  aortas,  to  all  parts  of  the  body.  After 
bathing  the  body-tissues  the  blood  is  collected  into  a 
median  longitudinal  vein  beneath  the  pericardium  called 
the  vena  cava.  From  the  vena  cava  the  blood  passes 
through  the  kidneys  and  gills  to  be  returned  at  last  to  the 
heart.  The  mantle  acts  as  an  organ  for  the  aeration  of 
the  blood,  and  the  blood  it  receives  or  at  least  part  of  it 
passes  directly  back  to  the  heart  without  passing  through 
the  kidneys  and  gills. 

Note  the  delicate  membranous  dark-colored  sac  on  the 
floor  of  the  pericardium,  the  kidneys  or  nepJiridia.  These 
are  paired  structures  which  appear  as  two  U-shaped  tubes 
lying  side  by  side.  Each  consists  of  a  lower  portion  with 
thick  folded  walls,  the  kidney  proper,  and  an  upper  thin- 
walled  portion,  the  ureter.  The  kidneys  open  internally 
through  a  pair  of  reno-pericardial  openings  into  the  peri- 
cardium, while  the  ureters  communicate  with  the  mantle- 
cavity  by  an  opening  on  the  side  of  the  body  beneath  the 
gills  as  already  mentioned.  The  kidneys  are  profusely 
supplied  with  fine  blood-vessels  and  carry  off  the  waste 
matter  from  the  blood. 


MOLLUSCS:    THE  MOLLUSCS  243 

Beneath  the  posterior  adductor  muscles  note  a  small 
white  spider-shaped  body,  the  more  or  less  united  visceral 
ganglia  of  the  nervous  system.  Posteriorly  these  ganglia 
give  off  nerves  to  the  mantle  and  gills,  while  anteriorly 
there  proceed  two  nerves,  the  ccrcbro-visceral  connectives, 
running  forward,  one  on  either  side  of  the  foot  close  to 
the  visceral  mass,  to  the  cerebro-pleural  ganglia,  paired 
ganglia  lying  near  the  mouth.  A  delicate  commissure 
running  over  the  gullet  connects  these  ganglia. 

TECHNICAL  NOTE. — Cut  away  the  skin  and  outer  muscular  layer 
from  the  left  side  of  the  foot. 

Note  the  large  stomach-cavity,  surrounded  by  the 
digestive  gland.  Trace  the  convolutions  of  the  alimentary 
canal  through  the  foot  to  the  anal  exit.  Note  in  the 
anterior  portion  of  the  foot  a  fused  pair  of  ganglia  similar 
to  the  visceral  ganglia.  These  are  the  pedal  ganglia, 
which  are  connected  by  a  pair  of  delicate  commissures, 
the  cerebro-pedal  connectives,  with  the  cerebro-pleural 
ganglia.  Note  the  glandular  tissue  which  fills  the  cavity 
of  the  foot  and  surrounds  the  loops  of  the  alimentary 
canal.  This  is  the  reproductive  organ,  which  has  its  exit 
leneath  the  gills  on  each  side  of  the  foot.  The  sexes  of 
ihe  mussel  are  separate,  but  the  reproductive  organs  are 
very  similar. 

Life-history  and  habits. — The  eggs  (ova)  of  the  female 
pass  first  into  the  supra-branchial  chamber,  whence,  after 
being  fertilized,  they  drop  into  the  outer  pair  of  gill- 
chambers.  These  outer  gills  serve  as  brood-pouches,  and 
here  it  is  that  the  embryonic  stages  are  passed  through. 
The  embryo  when  ready  to  issue  has  a  soft  body  enclosed 
in  two  triangular  valves.  At  this  stage  it  is  called  a 
glochidium.  The  glochidium  on  being  discharged  through 
the  exhalant  siphon  of  the  parent  fails  to  the  bottom, 
where  it  remains  for  a  time,  when  it  attaches  itself  to  some 


2,44  ELEMENTARY  ZOOLOGY 

fish  by  the  lower  hook-like  projections  of  the  valves  and 
leads  a  truly  parasitic  life  for  two  months,  after  which  it 
undergoes  a  metamorphosis  and  falls  to  the  bottom  again, 
there  to  begin  an  independent  existence.  Mussels  often 
congregate  in  favorite  mud  or  sand  banks.  Their  food 
consists  primarily  of  small  organisms,  both  plants  and 
animals,  which  are  taken  from  the  water  entering  the 
mantle-cavity.  Mussels  move  about  slowly  over  the 
muddy  bottom  of  the  stream  by  means  of  the  muscular 
foot. 

OTHER    MOLLUSCS. 

The  branch  Mollusca  includes  the  fresh-water  mussels, 
the  clams,  oysters,  snails,  and  slugs,  the  cuttlefishes,  and 
all  that  host  of  animals  we  call  ' '  shells  ' '  or  shell-fish,  which 
we  know  familiarly  only  by  the  shell  which  they  make, 
live  in,  and  leave  at  death  to  tell  the  tale  of  their  exist- 
ence. Not  all  the  molluscs,  however,  form  shells,  that 
is,  external  shells  which  serve  as  houses.  The  familiar 
slugs  do  not,  nor  do  a  number  of  ocean  forms  called 
nudibranchs,  which  are  somewhat  like  the  land-slugs,  only 
much  prettier  and  more  attractive.  All  the  cuttlefishes 
and  octopi  are  also  without  the  hard  calcareous  shell. 
But  most  of  the  molluscs  are  shell-bearing  animals.  The 
shell  may  be  bivalved,  as  in  the  mussel  and  clam,  or  uni- 
valved,  that  is,  composed  of  a  single  piece  which  may  be 
spirally  twisted,  as  with  the  snail,  or  otherwise  curiously 
shaped.  The  variety  in  the  form,  colors,  and  markings 
of  the  shells  indicates  the  great  diversity  among  molluscs. 
Molluscs  live  on  land,  in  fresh  water  and  in  the  ocean. 
No  depths  of  the  ocean  abysses  are  too  great  for  the 
octopi,  no  coast  but  has  its  many  shells,  hardly  a  pond 
or  stream  is  without  its  mussels  and  pond-snails,  and  in 
all  regions  the  land-snails  and  slugs  abound. 


MOLLUSCA  :   THE  MOLLUSCS  245 

Body  form  and  structure. — The  molluscs  are  not  to 
be  mistaken  for  any  other  of  the  lower  animals ;  they 
have  a  structure  peculiarly  their  own.  In  them  the  body 
is  not  articulated  or  segmented  as  with  the  worms  and 
arthropods,  nor  radiate  as  in  the  echinoderms,  nor  plant- 
like  as  with  the  sponges  and  polyps.  (Where  the  typical 
molluscan  body  is  well  developed  it  is  composed  of  four 
principal  parts:  a  head,  with  the  mouth,  feelers,  eyes,  and 
other  organs  of  special  sense;  a  trunk  containing  the 
internal  organs;  a  foot  which  is  a  thick  muscular  mass  not 
at  all  foot-  or  leg-like  in  shape,  but  which  is  the  organ 
of  locomotion  by  means  of  which  the  mollusc  crawls ;  and 
a  mantle  which  is  a  fold  of  the  skin  enclosing  most  of  the 
body  and  which  produces  the  shell.  Such  a  typical 
molluscan  body  is  possessed  by  most  of  the  snails.  But 
in  most  of  the  other  molluscs  one  or  more  of  these  four 
body-regions  are  so  fused  with  some  other  region  as  to 
be  indistinguishable.  In  the  mussels  and  clams  the  head 
is  not  at  all  set  off  from  the  rest  of  the  body,  the  cuttle- 
fishes and  octopi  have  no  foot,  the  slugs  have  no  shell.  In 
the  case  of  some  of  the  molluscs  without  external  shell  there 
are  inside  the  body  the  rudiments  or  vestiges  of  a  shell. 

With  regard  to  the  internal  organs  we  note  the  constant 
presence  of  three  pairs  of  ganglia,  viz.,  the  brain,  lying 
above  the  pharynx,  which  sends  nerves  to  the  feelers^ 
eyes,  and  auditory  organs ;  the  pedal  ganglion,  which  sends 
nerves  to  the  foot,  and  the  visceral  ganglion,  which  sends 
nerves  to  the  viscera.  This  is  a  condition  of  the  nervous 
system  characteristic  of  all  molluscs.  The  heart  is  a  well- 
developed  pulsating  sac  in  the  upper  part  of  the  body 
composed  of  either  two  or  three  chambers,  and  there  is  a 
well-defined  closed  system  of  arteries  and  veins,  specially 
complete  in  the  cuttlefishes  and  octopi.  This  highly 
developed  condition  of  the  circulatory  system  also  distin- 
guishes the  molluscs  from  the  other  invertebrates. 


246  ELEMENTARY  ZOOLOGY 

Development. — Reproduction  among  the  molluscs  is 
always  sexual.  Multiplication  by  budding  or  by  the 
parthenogenetic  production  of  eggs  is  not  known  to  occur. 
The  eggs  are  usually  laid  in  a  mass  held  together  by  a 
gelatinous  substance.  In  most  species  the  young  mollusc 
on  hatching  from  the  egg  does  not  resemble  its  parent, 
but  is  a  free-swimming  larva  called  a  vcliger.  It  is 
provided  with  cilia  for  organs  of  locomotion.  It  must 
undergo  a  radical  change  in  order  to  reach  the  adult 
stage.  Thus  metamorphosis  occurs  in  this  branch  as  well 
as  among  the  Arthropods  and  Echinoderms.  In  the 
development  of  some  molluscs,  however,  there  is  little  or 
no  metamorphosis,  the  young  being  hatched  in  a  condi- 
tion much  resembling,  except  in  size,  the  parent. 

Some  of  the  special  characteristics  of  structure,  life- 
history,  and  habits  of  the  molluscs  will  be  noted  in  our 
consideration  of  the  various  kinds. 

Classification. — The  branch  Mollusca  is  divided  into 
five  classes,  three  of  which  include  the  more  familiar 
kinds.  These  three  classes  are  the  Pelecypoda,  including 
the  mussels,  cockles,  clams,  scallops,  oysters,  etc.,  mol- 
luscs with  a  shell  composed  of  two  pieces,  one  on  each 
side  of  the  body  and  hinged  together;  the  Gastropoda, 
including  the  snails,  slugs,  periwinkles,  whelks,  and  a  host 
of  other  univalved  shell-fish,  that  is,  molluscs  which  have 
a  shell  composed  of  a  single  piece ;  and  the  Cephalopoda, 
including  the  squids,  cuttlefishes,  octopi,  and  the  pearly 
nautilus. 

Clams,  scallops,  and  oysters  (Pelecypoda).— TECHNICAL 

NOTE. — Shells  of  scallops,  oysters,  and  sea-rnussels  should  be  had  for 
examination  ;  also  specimens  of  Teredo  or  Pholas  in  alcohol  or  for- 
malin, and  pieces  of  pile  bored  by  Teredo.  Make  drawings  of  vari- 
ous bivalve  shells,  and  of  Teredo. 

The  fresh-water  mussel  which  we  have  studied  is  an 
example  of  the  bivalve  molluscs.  The  members  of  this 


hinge  ligamt 


reno-pericardial  aperture 

renal  aperture  v 
genital  aperture    ^ 


right  auricle  i 

anterior  aorta  \  , 


umbone- 


hinge  tooth 


stomach- 
digestive  gland 


gullet- 

wrebro-pleural  ganglion  -  ->• 
mouth / 


anter  adductor*'  \ ••. 

; 
'. 

anter  retractor   ,'*\ 


pedal  ganglion. 


foof~ "-^ 


intestine*' 
typhlosole 


\  mm 

,$® 


FIG.  103. — Dissection  oa 


ventricle 


/  pericardium 


rectum 
/ 

^kidney 


palhal  aperture 
---  posterior  aorta 

post,  retractor 

post  adductor 
.— ~  amis 


mantle  cavity 
-water  mussel.  Unio  sp. 


- visceral  ga  nglion 

exhalant  siphon 
super  branchial  chamber 


-  right  gill  ^ 


inhalant  siphon 


'shell 


palliai  groove 


MOLLUSCS:    THE  MOLLUSCS  247 

class  show  a  range  in  size  from  the  little  fresh-water 
Cyclas  about  I  cm.  long  to  the  giant  clam  of  the  Indian 
and  Pacific  islands  "which  is  sometimes  60  cm.  (2  feet) 
in  length  and  500  pounds  in  weight."  They  show  also 
some  variety  in  the  form  and  appearance  of  the  shell,  but 
not  anything  like  the  degree  of  variety  shown  by  the 
shells  of  the  Gastropods. 

The  edible  clams  are  of  several  different  species.  The 
hard-shell  clam  (Venus  mercenaria),  or  "quohog  "as  it 
is  often  called,  is  found  along  the  Atlantic  coast  from 
Texas  to  Cape  Cod.  It  is  "common  on  sandy  shores, 
living  chiefly  on  the  sandy  and  muddy  plots,  just  beyond 
low-water  mark.  ...  It  also  inhabits  estuaries,  where  it 
most  abounds.  It  burrows  a  short  distance  below  the 
surface,  but  is  frequently  found  crawling  at  the  surface 
with  the  shell  partly  exposed. "  The  shells  of  this  edible 
clam  are  white.  The  soft-shell  clam  (My a  arenaria], 
"  the  clam  par  excellence,  which  figures  so  largely  in  the 
celebrated  New  England  clam-bake,  is  found  in  all  the 
northern  seas  of  the  world.  .  .  .  All  along  the  coasts  of 
the  eastern  States,  every  sandy  shore,  every  mud  flat,  is 
full  of  them,  and  from  every  village  and  hamlet  the  clam- 
digger  goes  forth  at  low  tide  to  dig  these  esculent 
bivalves.  The  clams  live  in  deep  burrows  in  the  firm 
mud  or  sand,  the  shells  sometimes  being  a  foot  or  fifteen 
inches  beneath  the  surface.  When  the  flats  are  covered 
with  water  his  clamship  extends  his  long  siphons  up 
through  the  burrow  to  the  surface  of  the  sand,  and 
through  one  of  these  tubes  the  water  and  its  myriads  of 
animalcules  is  drawn  down  into  the  shell,  furnishing  the 
gills  with  oxygen  and  the  mouth  with  food,  and  then  the 
water  charged  with  carbonic  acid  and  fcecal  refuse  is 
forced  out  of  the  other  siphon.  When  the  tide  ebbs  the 
siphons  are  closed  and  partly  withdrawn."  Ocean  clams 
and  mussels  have  furnished  food  for  man'  for  ages,  and 


248  ELEMENTARY  ZOOLOGY 

along  coasts  are  found  here  and  there  great  mounds 
made  of  heaps  of  clam-shells  which  have  become  covered 
over  with  soil  and  vegetation.  Such  mounds  are  the  old 
feasting-places  of  the  early  coast  inhabitants,  and  the 
archaeologist  often  finds  in  these  "kitchen-middens,"  as 


FlG.  104. — A  group  of  marine  Pacific  Coast  molluscs;  in  upper  left-hand 
corner.  Piirpura  saxicola;  next  to  the  right,  Littorina  scutiilata,', 
farthest  to  right,  limpets,  Acmara  spectrum;  left-hand  lower  corner, 
Mytilus  calif orni anus;  in  right-hand  lower  corner  the  black  shells  just 
above  the  large  clam-shell,  Chlorostomum  fitncbralc.  (From  living 
specimens  in  a  tide  pool  in  the  Bay  of  Monterey,  California.) 

they  are  called,  various  relics  of  the  early  natives  of  the 
continent. 

Even  more  widely  known  that  the  clams  are  the  oysters 
(Ostrea  virginiana],  also  members  of  this  class  of  mol- 
luscs. The  oyster  is  carefully  cultivated  by  man  in  many 
countries.  It  has  its  two  shells  or  two  shell-halves  dis- 
similar, one  valve  being  hollowed  out  to  receive  the  body, 
while  the  other  is  nearly  flat.  The  oyster  is  attached  to 
the  sea-bottom  by  the  outside  of  the  hollowed-out  valve. 
When  first  hatched  the  young  oyster  swims  freely  by 
means  of  its  cilia;  after  a  few  days  it  attaches  itself  to 


MOLLUSCA:    THE  MOLLUSCS  249 

some  solid  object  and  grows  truly  oyster-like.  Much  care 
has  to  be  taken  in  cultivating  oysters  to  furnish  proper 
conditions  for  growth  and  development.  The  young 
oysters  when  first  attached  are  called  '  *  spat ' ' ;  when  a 
little  older  this  "spat,"  now  called  "seed,"  may  be 
transplanted  to  new  beds,  which  are  stocked  in  this  way. 
In  fact  some  beds  have  constantly  to  be  thus  restocked, 
the  young  oysters  produced  on  them  not  finding  good 
places  to  attach  themselves,  and  so  swimming  away. 
Sometimes  pieces  of  slate,  pottery,  etc.,  are  strewed  about 
the  oyster-beds  to  serve  as  ' '  collectors, ' '  that  is,  as 
places  for  the  attachment  of  the  young  oysters.  The 


FIG.  105. — Dactylus  sp..   a  mollusc,  excavating  granite.     (Photograph  by 
C.  H.  Snow;  permission  of  Amer.  Soc.  Civil  Engineers.) 

extent  of  the  acreage  of  the  American  oyster-beds  is 
larger  than  that  .of  any  other  country.  "The  Baltimore 
oyster-beds  on  the  Chesapeake  River  and  its  tributaries 
cover  3,000  acres,  and  produce  an  annual  crop  of  25,000, - 
ooo  bushels." 

The  "  pearl-oyster  "  is  not  a  true  oyster,  that  is,  not  a 
member  of  the  family  to  which  the  edible  oysters  belong, 


250 


ELEMENTARY  ZOOLOGY 


but  it  is  a  member  of  the  same  class,  that  is,  it  is  a  bivalve 
mollusc.  Pearls  are  obtained  from  a  number  of  different 
"  pearl-oysters, ' '  but  the  finest  pearls  and  mother-of-pearl 
come  from  the  tropical  species  Meleagrina  margaritifera. 
This  pearl-oyster  "has  an  extensive  distribution,  being 
found  in  Madagascar,  the  Persian  Gulf,  Ceylon,  Australia, 
Philippine  Islands,  South  Sea  Islands,  Panama,  West 
Indies,  etc."  Mother-of-pearl  is  simply  the  inner  lining 
of  the  shell,  which  is  composed  of  numerous  thin  layers  of 
carbonate  of  lime  so  arranged  that  the  edges  of  the  suc- 
cessive layers  produce  many  fine  striae  very  close  together. 
The  beautiful  iridescence  of  this  inner  shell-lining  is 
caused  by  the  complicated  diffraction  and  reflection  (inter- 
ference effects)  of  the  light  by  the  fine  striae  and  the 
translucent  superposed  thin  plates  of  shell  material. 
Pearls  are  simply  isolated  deposits  of  shell  material  usually 
around  some  particle  of  foreign  substance  which  has  found 


FIG.  106. — Pholas  sp.,  a  mollusc,  burrowing  in  sandstone.     (Photograph 
by  C.  H.  Snow;  permission  of  Amer.  Soc.  Civil  Engineers.) 

lodging  in  the  mantle-cavity.  Sometimes  small  objects 
are  purposely  introduced  into  the  shell  in  order  to  stimu- 
late the  formation  of  pearls.  The  pearl-fishers  go  out  in 
boats  and  dive  to  the  bottom,  filling  baskets  with  pearl- 
oysters.  These  are  piled  up  in  a  bin  and  left  to  die  and 


MOLLUSC  A  :    THE  MOLLUSCS  251 

decompose.  "  When  the  flesh  is  pretty  thoroughly  dis- 
integrated, it  is  washed  away  with  water,  great  care  being 
taken  that  none  of  the  pearls  loose  in  the  flesh  are  lost. 
When  the  washing  is  concluded  the  shells  themselves  are 
examined  for  pearls  which  may  be  attached  to  the  interior 
of  the  valves. ' '  The  principal  pearl-fishery  is  that  on  the 
coast  of  Ceylon ;  pearl-fishing  has  been  carried  on  here 
for  over  2000  years. 

The  ship-worm  (Teredo)  is  an  interesting   member  of 
this    class    of  bivalve    molluscs,   because  of   its    unusual 


FIG.  107. — Martesia  xylophaga,  a  Pholad,  in  Panama  mahogany.     (Photo- 
graph by  C.  H.  Snow;  permission  of  Amer.  Soc.  Civil  Engineers.) 

habits,  and  strangely  modified  body  form.  The  teredo 
is  long  and  worm-like  in  general  appearance,  with  a  small 
bivalve  shell  at  one  end  and  two  elongated  siphons  at  the 
other.  The  young  teredo  is  a  free- swimming  ciliated 
embryo  like  the  young  of  the  other  bivalve  molluscs,  but 
it  soon  settles  on  a  piece  of  submerged  wood,  usually  the 
pile  of  a  wharf,  or  the  bottom  of  a  ship,  and  burrows  into 
this  wood.  As  it  grows  it  enlarges  and  deepens  its  tube- 
like  burrow,  and  lines  it  with  a  calcareous  deposit.  The 
burrow  may  be  a  foot  long  or  longer,  and  when  thousands 
of  teredos  attack  a  pile  or  the  bottom  of  a  ship,  the  wood 
soon  becomes  riddled  with  holes.  These  boring  molluscs 


252  ELEMENTARY  ZOOLOGY 

do  great  damage  to  wharves  and  ships.  In  Holland 
where  they  were  first  discovered  they  caused  such  injuries 
to  the  piles  and  other  submerged  wood  which  supported 


FIG.  108. — The  giant  yellow  slug  of  California,  Ariolimax  californica. 
This  slug  reaches  a  length  when  outstretched  of  13  inches.  (From 
living  specimen.) 

the  dikes  and  sea-walls  that  they  seriously  threatened  the 
safety  of  the  country. 

Snails,  slugs,  nudibranchs  and  "  sea-shells  "  (Gas- 
tropoda).— TECHNICAL  NOTE. — Pond-snails  can  be  readily  found 
clinging  to  submerged  stems,  leaves,  or  pieces  of  wood  in  almost 
any  pond.  Collect  some  and  carry  alive,  in  a  jar  of  water,  to  the 
schoolroom.  Observe  the  habits  of  these  live  snails  in  the  school  aqua- 
rium. Note  the  movements,  the  coming  to  the  surface  to  breathe, 
the  eating  (by  scraping  the  surface  of  the  leaves  with  the  "  radula  " 
or  tongue  ;  provide  fresh  bits  of  cabbage  or  lettuce-leaves),  the  "use 
of  the  feelers.  Make  drawings  illustrating  these  habits.  Examine 
the  shell  ;  note  that  it  is  univalved,  that  is,  composed  of  one  piece. 
Do  the  whorls  of  all  the  shells  turn  the  same  way  ?  Make  a  draw- 
ing of  the  shell,  naming  such  parts  as  the  apex,  spire  (all  the  whorls 
taken  together),  the  aperture,  the  columella  (the  axis  of  the  spire), 
the  lip  (outer  edge  of  the  aperture),  the  lines  of  growth  (parallel  to 
the  tip),  the  suture  (the  spiral  groove  on  the  outside).  Examine  the 
snail  ;  note  the  character  of  the  foot  ;  note  the  protrusible  tentacles 
or  feelers,  the  eyes  (dark  spots  at  bases  of  the  tentacles),  the  mouth, 
the  respiratory  opening  (on  right  side  of  body  in  the  edge  of  the 
mantle  which  protrudes  beneath  the  lip  when  the  snail's  body  is  ex- 
tended), the  radula  or  ribbon-like  tongue  with  fine  teeth.  Compare 
with  the  body  of  the  mussel. 

Slugs  may  be  found  during  the  day  concealed  under  boards  or 
elsewhere  ;  they  are  nocturnal  in  habit.  If  specimens  can  be  ob- 
tained, compare  with  the  pond-snails,  noting  the. absence  of  a  shell, 
and  the  fleshy  mantle  on  the  dorsal  surface  near  the  head  ;  note  the 
presence  of  two  pairs  of  tentacles  (the  eyes  being  at  the  tips  of  the- 


MOLLUSC/I:   THE  MOLLUSCS  253 

^ 

second  or  hinder  pair),  and  the  respiratory  pore.     Note  the  streak 
of  mucus  left  by  the  slugs  in  crawling  about. 

Some  sea-shells  can  be  got  from  private  collections  of"  curios" 
to  illustrate  the  variety  of  form  of  the  univalve  shells. 

Perhaps  one-half  of  all  the  known  species  of  molluscs 
are  snails  and  slugs  (fig.  108).  Snails  are  either  aquatic  or 
terrestrial  in  habit,  but  in  either  case  they  (the  true  pulmo- 
nate  snails)  breathe  not  by  means  of  gills,  as  do  most  of 
the  other  molluscs,  but  by  means  of  a^so-^alled  "lung." 
This  lung  is  a  sac  with  an  external  Opening  on  the  right 
side  of  the  body  and  with  its  inner  surface  richly  furnished 
with  fine  blood-vessels.  The  exchange  of  gases  between 
the  blood  and  the  outer  air  takes  place  through  the  thin 
walls  of  the  blood-vessels.  Most  snails  which  live  in  the 
water,  as  the  pond-snails  and  the  river-snails,  have  to 
come  occasionally  to  the  surface  to  breathe.  These  fresh- 
water and  land -molluscs  which  possess  a  lung-sac  instead 
of  gills  constitute  the  order  Pulmonata.  The  pulmonate 
pond-  and  land-snails  and  slugs  are  vegetable  feeders  and 
where  they  occur  in  large  numbers  do  much  injury  to 
vegetation.  While  the  common  pond-snails  have  but 
one  pair  of  feelers,  at  the  base  of  which  are  found  the 
eyes,  most  of  the  land-snails  and  slugs  have  two  pairs  of 
' '  horns, ' '  the  eyes  being  on  the  tips  of  the  second  pair. 
The  lung-sac,  besides  serving  as  a  breathing  organ,  also 
enables  the  snail  to  rise  or  sink  according  as  the  animal 
varies  the  size  of  the  sac  and  consequently  the  amount  of 
air  in  it.  All  the  Pulmonata  are  hermaphroditic,  each 
individual  producing  both  sperm-  and  egg-cells.  The 
eggs  of  the  pond-snail  ' '  are  laid  in  gelatinous  transparent 
capsules,  half  .an  inch  to  an  inch  in  length,  flattened  and 
linear  or  oblong  in  outline.  After  a  few  snails  have  been 
kept  a  short  time  in  a  small  'vessel  of  water  with  their 
appropriate  food,  these  egg-capsules  may  be  looked  for 
on  the  bottom  and  sides  of  the  vessel  or  closely  adherent 


254  ELEMENTARY  ZOOLOGY 

to  the  stems  or  leaves  of  plants  placed  in  the  water. 
They  are  so  transparent  as  to  be  easily  overlooked. ' ' 
Young  snails  may  be  reared  from  these  eggs. 

There  are  other  snails  common  in  ponds,  also  called, 
like  the  pulmonate  forms,  pond-snails,  which  have  gills 
and  no  lung-sac.  These  pond-snails  belong  to  a  different 
order  of  molluscs,  and  live  on  the  bottom  of  the  pond, 
crawling  about  in  the  soft  mud  and  feeding  on  animal 
instead  of  vegetable  food. 

The  shells  of  the  various  kinds  of  snails  vary  much. 
In  many  of  the  land-snails  the  spiral  is  not  spire-shaped 
or  conical,  but  is  flat.  In  some  the  whorls  of  the  spiral 
run  from  left  to  right  (dextral)  when  the  shell  is  looked 
at  with  apex  held  toward  one,  while  in  others  the  whorls 
run  from  right  to  left  (sinistral). 

Of  the  hosts  of  marine  Gastropods  we  can  notice  only 
a  few  kinds.  The  nudibranchs  (fig.  109)  are  a  group  of 


FIG.  109. — Three  Pacific  Coast  nudibranchs;  Doris  tuberculata  (in  lower 
left-hand  corner),  Echinodoris  sp.  (upper  one),  and  Triopha  modesta 
(at  right).  (From  living  specimens  in  a  tide-pool  on  the  Bay  of  Mon- 
terey, Califorria.) 

beautiful  forms  in  which  the  shell  is  wholly  wanting  and 
the  mantle  is  usually  absent.  The  gills  are  thus  exposed 
and  are  usually  in  the  shape  of  delicate  freely  projecting 


MOLLUSC  si;    THE  MOLLUSCS  255 

tufts  arranged  in  rows  along  the  back.  The  body  is  often 
strikingly  and  variedly  colored.  These  soft,  naked  "  sea- 
slugs  ' '  live  near  the  shore,  creeping  about  among  the 
rocks  and  seaweeds.  About  a  thousand  species  of  nudi- 
branchs  are  known. 

Among  the  shell-forming  marine  Gastropods  there  is 
great  variety  in  the  size  and  shape  and  coloring  of  the 
shells.  Many  are  beautifully  colored  and  patterned ; 
others  are  oddly  and  fantastically  shaped.  The  cowries, 
or  porcelain  shells,  familiar  in  collections  of  ocean  curiosi- 
ties, have  a  large  body  whorl  and  a  very  short  flat  spire, 
and  the  brightly  colored  shell  looks  as  if  enamelled. 
Some  of  the  coast  tribes  of  Africa  once  used,  and  perhaps 
still  use  to  some  extent,  cowries  as  money.  The  limpets 
(fig.  104)  are  among  the  most  abundant  of  the  seashore 
molluscs,  their  low,  broadly  conical  shells  being  plenti- 
fully scattered  over  the  rocks  between  tide-lines.  The 
* '  oyster-drills  ' '  are  Gastropods  with  odd  spiny  shells  which 
do  much  harm  in  oyster-beds  by  settling  down  on  the 
oysters,  boring  holes  through  the  shells  and  eating  the 
soft  parts  within.  The  helmet-shells,  from  which  shell 
cameos  are  cut,  are  composed  of  layers  of  shell  material 
of  different  colors.  Among  the  specially  beautiful  shells 
are  the  cone-shells,  the  olive-shells,  the  ivory-shells,  etc. 

Squids,    cuttlefishes,   and   octopi    (Cephalopoda).— 

TECHNICAL  NOTE. — Small  squids  preserved  in  alcohol  or  formalin 
can  be  had  of  all  dealers  in  biological  supplies  (see  p.  453),  and 
specimens  should  be  examined. 

The  squids  (fig.  no),  cuttlefishes,  octopi  or  "devil- 
fishes," and  the  three  living  species  of  Nautilus  constitut- 
ing the  class  Cephalopoda  are  very  different  from  the  other 
molluscs  in  appearance,  and  are  in  fact  different  in  im- 
portant structural  characters.  They  can  move  swiftly, 
have  strangely  modified  organs  of  prehension,  strong  biting 
mouth-parts,  and  eyes  of  very  complex  organization. 


256  ELEMENTARY  ZOOLOGY 

They  are  the  most  highly  organized  molluscan  forms,  and 
their  predaceous  habits  and  the  great  size  to  which  some 
of  them  attain  have  given  them  distinction  among  the 
fierce  and  dangerous  creatures  of  the  sea.  They  are  all 
strictly  marine  in  habitat,  and  are  all  carnivorous.  Most 
of  them  have  no  shell,  or  where  the  shell  is  present  it  is 
internal  in  all  but  a  very  few  forms.  The  tentacle-like 
arms  or  feet  surrounding  the  mouth  which  occur  in  all  the 
Cephalopods  are  provided  with  sucking  organs  or  suckers, 
in  some  cases  with  a  horny  toothed  rim.  These  long, 
powerful,  grasping,  tentacular  feet,  with  the  suckers  and 
five  hooks,  are  very  effective  means  of  securing  prey,  and 
the  pair  of  strong,  sharp,  cutting  mandibles  or  beaks  are 
equally  effective  in  tearing  to  pieces.  The  eyes  of  the 
Cephalopods  are  almost  as  highly  developed  as  those  of 
the  vertebrates.  They  are  unusually  large  and  staring, 
and  add  much  to  the  terrifying  appearance  of  the  "  devil- 
fishes." Cephalopods  have  the  power  of  quickly  chang- 
ing color,  because  of  the  presence  in  the  skin  of  many 
pigment-cells  which  can  expand  so  as  nearly  to  touch 
each  other,  thus  producing  a  uniform  tint  over  the  whole 
body,  or  which  can  contract  so  as  to  destroy  this  uniformity 
of  color.  There  are  several  sets  of  these  color-carrying 
cells  or  chromatophores,  each  set  of  a  color  different  from 
the  others.  The  purpose  of  this  change  of  color  is  pro- 
tective, the  animal  being  thereby  able  to  make  its  color 
so  harmonize  with  that  of  its  immediate  surroundings  as 
to  become  indistinguishable. 

There  are  two  principal  groups  of  Cephalopods,  viz., 
the  Decapods  and  the  Octopods.  The  Decapods,  as  their 
name  indicates,  have  ten  feet  or  arms  surrounding  the 
mouth,  and  in  them  the  body  is  usually  elongate,  con- 
taining a  horny  "pen"  or  calcareous  "bone."  This 
group  includes  the  cuttlefishes  or  sepias,  from  which  are 
obtained  sepia  ink  and  the  cuttlefish  bone  used  to  feed 


MOLLUSCS:    THE  MOLLUSCS  257 

canary  birds.  The  ink  is  a  secretion  which  the  cuttlefish 
discharges  when  attacked  to  create  a  cloud  in  the  water 
and  thus  escape  unperceived.  The  squids  (Loligo)  com- 
monly used  as  bait  by  fishermen  belong  to  the  Decapoda. 
The  two  extra  feet  or  arms  which  the  Decapods  have  in 
addition  to  the  eight  possessed  by  the  Octopods,  differ 
from  the  others  in  being  longer  and  slenderer  and  having 
suckers  only  on  the  distal  extremities  which  are  expanded 
into  "clubs  "  (fig.  no). 

The  Octopods  have  a  short,  sac-like,  sub- spherical  body 
and  neither  external  nor  internal  shell.      To  this  group 


FlG.  I  jo. — The  giant  squid,  Ommatostrephes  californica.  (From  specimen 
with  body  (exclusive  of  tentacles)  four  feet  long,  thrown  by  waves  on 
shore  of  the  Bay  of  Monterey,  California.) 

belong  the  famous  devil-fishes  (Octopus],  whose  strange 
and  terrifying  appearance  combined  with  their  frequently 
great  size  has  furnished  the  basis  for  many  a  weird  tale  of 
the  sea.  Octopi  have  been  killed  having  tentacles  more 
than  30  feet  in  length.  The  largest  members  of  the 
class,  however,  are  probably  the  giant  squids  (belonging 
to  the  Decapoda)  specimens  of  which  have  been  captured 
with  a  body-length  of  twenty  feet,  and  arms  thirty-five 
feet  long. 

The  beautiful  paper  sailor  or  argonaut  (Argonauta  argo). 


258  ELEMENTARY  ZOOLOGY 

which  secretes  a  thin  shell  (not  homologous  with  the 
shell  of  the  other  molluscs)  to  protect  her  eggs,  is  a  mem- 
ber of  the  Octopod  group.  In  fine  weather  the  argonauts 
sail  in  fleets  on  the  surface  of  the  ocean. 

The  pearly  nautilus  (Nautilus  pompilius)  is  a  Cephalo- 
pod  with  four  gills  instead  of  two,  as  with  the  Decapoda 
and  Octopoda,  and  is  the  only  existing  member  of  what 
was  in  the  earlier  times  of  the  earth's  history  a  large 
group  of  animals.  The  nautili  live  in  rather  shallow 
water  usually  creeping  over  the  bottom  feeding  on  small 
marine  animals.  They  make  a  many-chambered  spiral 
shell  with  its  inner  surface  lined  with  beautiful  pearly 
nacre. 


CHAPTER  XXIII 

BRANCH    CHORDATA:      THE    VERTEBRATES, 
ASCIDIANS,  ETC. 

THE  branch  Chordata  includes  all  the  backboned 
animals  or  vertebrates,  comprising  the  fishes,  salamanders, 
frogs  and  toads,  lizards,  crocodiles,  turtles  and  snakes, 
birds,  and  all  the  quadrupeds  or  mammals,  and  includes 
also  a  few  small  unfamiliar  ocean  animals  which  do  not 
look  at  all  like  the  backboned  animals,  but  which  agree 
with  them  in  possessing  a  peculiar  structure  called  the 
notochord.  This  notochord  consists  of  a  series  or  cord  of 
cells  extending  longitudinally  through  the  body  from  head 
to  tail,  above  the  alimentary  canal  and  below  the  spinal 
nerve-cord.  In  all  the  vertebrates  excepting  a  few  low 
forms,  the  notochord  while  present  in  the  young,  is  re- 
placed in  the  adult  by  a  segmented  bony  or  cartilaginous 
axis,  the  spinal  or  vertebral  column.  But  in  the  ascidians 
or  sea-squirts  (called  also  tunicates)  it  persists  throughout 
life.  In  addition  to  this  characteristic  notochord,  nearly 
all  the  Chordata  are  marked  by  the  presence,  either  in 
embryonic  or  larval  stages  only,  or  else  persisting  through- 
out life,  of  a  number  of  slits  or  clefts  in  the  walls  of  the 
pharynx  which  serve  for  breathing,  and  which  are  called 
gill-slits. 

Structure  of  the  vertebrates. — As  the  backboned  or 
vertebrate  animals  make  up  almost  the  whole  of  the 
branch  Chordata,  and  as  the  few  other  chordates  are 
animals  the  special  structures  of  which  we  shall  not  under- 
take to  study  in  this  book,  we  may  note  here  some  of  the 
other  more  obvious  structural  characteristics  of  the  true 

259 


260  .ELEMENTARY  ZOOLOGY 

vertebrates.       The    possession    of   a   backbone    or    bony 
(sometimes  cartilaginous)  spinal  column  is  the  character- 
istic by  which  we  distinguish  them  from  the  invertebrate 
or  backboneless  animals.      Furthermore,  all  of  the  verte- 
brates possess  an  internal  skeleton  which  is  in  most  cases 
composed  of  bone,  and  is  firm  and  strong.     In  some  of  the 
lower  fishes,  as  the  sharks  and  sturgeons,  the  skeleton  is 
made  up  of  cartilage,  tough  but  not  hard.     The  vertebrate 
skeleton  consists  typically  of  an  axial  portion  comprising 
the  spinal  column  and  head,  and  of  two  pairs  of  append- 
ages or  limbs,   variously  developed  as  fins,   wings,   legs 
and  arms.      In  some  vertebrates  these  limbs  are  repre- 
sented  by   mere  rudiments,    and   in   the  lowest  fish-like 
forms,    the    lancelets    and    lampreys,    there    is    not    the 
slightest  trace  of  limbs.      A  part  of  the   central  nervous 
system,  the  spinal  cord,  runs   longitudinally  through  the 
body  on  the  dorsal  side  of  the  alimentary  canal ;  the  cir- 
culatory system  is  closed,  the  blood  being  always  confined 
in  the  heart  and  in  vessels  called  arteries,  veins,  and  capil- 
laries, and  the  blood  is  red  in  color  owing  to  the  presence 
of  numerous  red  corpuscles  or  blood-cells.      The  nervous 
system  is  highly  developed,  with  a  large  brain  in  all  the 
typical  forms,   and    with     complex    and     usually    highly 
efficient  special  sense-organs.      Respiration  is  carried  on 
by  means  of  external  gills,  or  by  internal  lungs  which 
communicate   with  the    outside  through    the    mouth   and 
nostrils.      To  the   lungs  and  gills  the  blood  is  brought  to 
be  "purified,"  i.e.,  to  give  up  its  carbonic-acid  gas  and 
to  take  up  oxygen. 

Classification. — The  Chordata  are  variously  divided 
by  zoologists  into  eight  or  ten  classes,  of  which  (in  the 
eight-class  system)  the  five  classes*  Pisces  (fishes), 

*  The  animals  included  by  some  zoologists  in  the  single  class  Pisces,  are 
held  by  other  zoologists  to  constitute  three  distinct  classes,  thus  making  a 
subdivision  of  the  branch  into  ten  classes. 


BRANCH  CHORD  AT  A :   THE   VERTEBRATES,  ETC.       261 

Batrachia  (batrachians),  Reptilia  (reptiles),  Aves  (birds), 
and  Mammalia  (mammals),  belong  to  the  true  vertebrates. 
These  classes  will  be  considered  in  the  five  following 
chapters. 

The  remaining  three  classes  include  a  number  of  strange 
marine  forms  which  until  recent  years  were  considered  as 
worms,  but  which  are  now  known  to  be  the  nearest  living 
allies  of  the  earliest  or  primitive  vertebrates.  The  rela- 
tionship of  these  forms  to  early  types  is  manifest,  not  in 
the  appearance  or  structure  of  the  adult  stage,  but  only 
during  embryonic  or  larval  stages. 

The  ascidians. — The  sea-squirts,  or  Ascidians,  com- 
mon on  the  seashore,  compose  one  class  of  these  primitive 


FIG.  m.-^-An  ascidian  or  sea-squirt  from  the  coast  of  California.     (After 
Jordan  and  Kellogg.) 

chordate  animals.      They  possess  a  simple,  sac-like  body 
(fig.  ill),  fastened  to  the  rocks  by  one  end,  the  other  being 


262  ELEMENTARY  ZOOLOGY 

provided  with  two  openings,  one  for  the  ingress  and  the 
other  for  the  exit  of  water,  a  strong  current  of  which  flows 
constantly  through  the  body.  By  means  of  this  current 
the  ascidian  obtains  food.  Usually  sea-squirts  live 
together  in  large  colonies,  and  in  some  cases  a  number  of 
individuals  enclose  themselves  in  a  common  gelatinous 
mass,  forming  what  is  called  a  compound  ascidian. 

The  ascidian  when  born  is  a  tiny,  free-swimming,  tad- 
pole-like creature  with  a  slender  finned  tail.  It  swims 
about  freely  for  only  a  few  hours,  however,  soon  attach- 
ing itself  to  a  rock,  and  in  its  further  development  becom- 
ing degenerate.  It  loses  its  tail  and  with  it  the  short 
notochord  possessed  by  the  larva;  the  eye  and  the  auditory 
organ  are  lost,  and  the  nervous  system  and  alimentary 
canal  become  much  reduced  and  simplified.  Sea-squirts 
in  their  adult  stage  are  very  simple  degenerate  animals, 
with  low  functional  development,  yet  their  embryonic  and 
larval  conditions  show  a  considerable  degree  of  structural 
specialization,  and  the  presence  of  the  notochord  in  these 
early  stages  reveals  their  affinity  with  the  backboned 
animals. 


CHAPTER  XXIV 

BRANCH  CHORDATA  (Continued}'.  CLASS  PISCES 
(THE    FISHES) 

THE  GOLDEN  SUNFISH  OR  PUMPKIN  SEED  (Apomotts  sp.) 

TECHNICAL  NOTE. — The  species  of  sunfish  named,  or  some  closely 
related  species,  can  be  obtained  in  any  brook  or  stream  in  the 
United  States.  Gibbosus  lives  in  all  streams  north  of  Dubuque, 
Chicago,  Pittsburg,  and  along  the  eastern  coast  north  of  Charleston. 
Closely  allied  species  live  in  all  the  other  parts  of  the  countn 
except  in  the  higher  Rocky  Mountains  west  of  Bismarck,  Pueblo, 
and  Santa  Fe.  One  species  is  found  in  the  streams  of  California, 
but  none  occurs  in  Washington  or  Oregon.  In  the  few  places 
where  a  sunfish  cannot  be  had,  any  species  of  bass  or  perch  may 
be  used.  Sunfish  live  in  ponds  and  sluggish  streams  in  deep  holes 
under  a  log  or  at  the  foot  of  a  stump.  They  take  eagerly  a  hook 
baited  with  a  worm,  or  they  may  be  caught  in  nets.  When  sun- 
fish  cannot  be  kept  fresh  for  study  in  class,  specimens  may  be 
preserved  in  alcohol  or  4^  formalin.  But  if  possible  to  keep  some 
alive  for  a  time  in  a  jar  or  tub  with  plenty  of  fresh  water,  the  colors 
of  the  living  fish,  together  with  its  manner  of  swimming  and  mode 
of  breathing,  can  be  observed. 

External  structure*  (fig.  1 12). — Examine  the  general 
configuration  and  make-up  of  the  body.  Note  the  deep, 
laterally  flattened  trunk  and  paddle-like  tail.  The  head 
is  closely  fitted  to  the  trunk  without  any  neck.  Note  that 

*  The  author  wishes  to  call  the  attention  of  teacher  and  student  to  the 
plan  (referred  to  in  the  Preface,  page  v)  adopted  in  writing  the  directions 
for  the  dissections.  The  sequence  of  the  references  to  the  various  organs 
depends  on  the  actual  course  of  the  dissection,  and  not  upon  the  association 
of  organs  in  systems.  And  the  directions  are  so  much  condensed  that  they 
are  hardly  more  than  a  means  of  orienting  the  student,  leaving  him  to  work 
out  independently,  or  by  the  aid  of  more  detailed  accounts  (sometimes 
specifically  referred  to),  the  details  of  the  dissection. 

263 


264  ELEMENTARY  ZOOLOGY 

the  body  is  thickly  covered  with  firm,  hard  scales,  arranged 
like  the  shingles  on  a  roof.  Remove  one  of  these  scales 
and  examine  it  under  a  hand  lens.  What  sort  of  an  edge 
has  it  ?  Such  a  scale  is  said  to  be  ctenoid. 

The  body  of  the  sunfish  terminates  behind  in  the 
caudal  fin,  a  series  of  cartilaginous  rays  connected  by  thin 
skin  and  attached  to  a  bony  plate  at  the  end  of  the  back- 
bone. Along  the  median  dorsal  line  will  be  noted  another 
fin  composed  anteriorly  of  spines  and  posteriorly  of  soft 
rays  jointed  and  branched.  This  is  the  dorsal  fin.  How 
many  spines  has  it  ?  Anterior  to  the  caudal  fin  on  the 
ventral  surface  is  a  median  unpaired  anal  fin.  How  many 
spines  has  it  ?  Anterior  to  the  anal  fin  are  the  ventral 
fins,  while  on  the  sides  of  the  body  back  of  the  head  in 
a  line  with  the  mouth  are  found  the  pectoral  fins.  The 
ventral  fins,  attached  to  a  rudimentary  pelvis,  correspond 
to  the  hind  legs  of  the  other  vertebrates.  The  pectoral 
fins,  attached  to  the  shoulder  girdle,  correspond  to  the 
arms.  In  front  of  the  anal  fin  note  a  small  pit-like  open- 
ing, the  opening  from  the  kidneys  and  reproductive  organs, 
and  just  anterior  to  this  a  large  aperture,  the  amis.  At  the 
anterior  end  of  the  head  note  the  broad  moutli,  surrounded 
by  a  complicated  system  of  bones.  Note  the  large  eyes 
surrounded  by  a  series  of  small  bones,  the  orbital  chain. 
Just  anterior  to  the  eyes  are  two  pairs  of  openings,  one 
pair  of  each  side  opening  into  a  closed  sac.  What  are 
these  openings  ?  Note  the  presence  of  various  bones  on 
the  side  of  the  head,  each  covered  with  a  thin  layer  of 
skin.  These  are  membrane  bones,  characteristic  of  fishes. 
Are  there  any  external  ears  in  the  fish  ?  Examine  the  in- 
side of  the  mouth.  Is  there  a  tongue  f  If  so,  of  what  char- 
acter ?  Are  there  teeth  f  If  so,  where  are  they  situated  ? 

Note  along  each  side  extending  to  the  base  of  the  tail 
a  line  of  modified  scales,  on  each  scale  a  little  mucous 
tube,  the  whole  series  constituting  the  lateral  line.  These 


BRANCH  CHORD  AT /I;   CLASS  PISCES:   THE  FISHES     265 

scales  are  intimately  associated  with  a  large  nerve  (the 
vagifs),  and  probably  serve  an  important  part,  not  yet 
clearly  understood,  in  the  life  of  the  fish. 

Lift  up  the  flap  in  front  of  one  of  the  pectoral  fins. 
This  is  the  opercular  flap  which  covers  the  gills  that  lie 
beneath.  Bend  this  forward  and  find  four  gill-arches, 
each  with  its  double  fringe  of  gills.  Note  the  gill-rakers, 
short  and  blunt,  on  the  first  gill-arch.  Note  also  on  the 
under  side  of  the  flaps  turned  back,  delicate  red  gill-like 
structures  covered  by  a  membrane.  These  are  t\\z  false 
gills  or  psendo-branchice,  larger  in  most  fishes  than  in  the 
sunfish.  The  gills  in  the  fish  subserve  the  same  function 
as  the  gills  of  the  crayfish,  that  of  purifying  the  blood 
by  eliminating  carbonic-acid  gas  from  it  and  taking  up 
oxygen  from  the  air  mixed  with  or  dissolved  in  the  water. 
Organs  subserving  the  same  purposes  in  different  kinds  of 
animals  as,  for  example,  the  gills  in  fish  and  in  crayfish, 
are  called  analogous  structures.  But  there  is  an  important 
morphological  difference  between  the  fish's  gills  and  the 
gills  of  the  crayfish.  In  the  latter  animal  they  are  out- 
growths of  the  basal  segments  of  the  walking-legs ;  in  the 
fish  they  are  outgrowths  from  the  alimentary  canal.  The 
internal  gills  of  the  young  toad  (tadpole)  arise  in  the  same 
way  as  those  of  a  fish.  Structures  which  are  identical  in 
their  origin,  like  the  gills  of  tadpole  and  fish,  are  called 
Jioinologous  structures. 

Make  a  drawing  of  the  sunfish  from  a  lateral  aspect, 
showing  the  external  parts  named. 

Internal  structure. — TECHNICAL  NOTE. — Insert  one  point 
of  the  scissors  a  little  to  one  side  of  the  anus  and  cut  dorsally  on  the 
left  side  of  the  body  to  the  backbone.  Now  cut  anteriorly  from  the 
anus  along  the  ventral  wall  to  where  the  jaws  unite,  and  cut,  also 
anteriorly,  along  the  dorsal  wall  until  the  left  side  of  the  body  can 
be  removed.  Bend  the  opercular  flap  backward  over  the  eye  and 
pin  the  entire  fish,  uncut  side  down,  to  the  bottom  of  the  dissecting- 
pan,  covering  it  with  water. 


266  ELEMENTARY  ZOOLOGY 

The  above  operation  will  have  severed  the  large  power- 
ful muscles  forming  the  body-wall  and  extending  along 
the  sides.  Note  a  membranous  sac  completely  filling  a 
large  dorsal  cavity.  This  is  the  swim- bladder,  a  float 
filled  with  air  which  tends  to  give  the  fish  the  same  weight 
as  the  water  it  displaces.  It  arises  as  a  diverticulum  from 
the  alimentary  canal,  but  soon  becomes  permanently  shut 
off  from  it.  Beneath  the  swim-bladder  is  a  large  cavity 
filled  with  various  organs,  collectively  known  as  the 
viscera.  In  vertebrate  animals  the  cavity  which  contains 
the  viscera  is  generally  called  the  peritoneal  cavity.  It  is 
lined  by  the  peritoneum,  a  delicate  membrane,  part  of 
which  is  deflected  as  the  mesentery  over  the  alimentary 
canal  and  the  other  organs,  thus  suspending  them  all  from 
the  dorsal  wall.  Note  in  the  anterior  end  of  the  peritoneal 
cavity  a  large  bi-lobed  gland,  the  liver,  red  in  fresh, 
yellowish  in  alcoholic  specimens.  Its  function,  like  that 
of  the  liver  of  the  toad,  is  to  store  up  nutriment  for  the 
blood  and  to  secrete  a  digestive  fluid  called  bile.  Behind 
the  liver  note  a  long,  convoluted  tube.  What  is  this  tube  ? 
Unfold  this  tube,  separating  it  from  its  enveloping  mem- 
brane, the  mesentery.  Thrust  a  probe  down  the  throat 
and  note  that  it  passes  into  a  thick-walled  sac,  the 
stomach.  The  mouth  and  gill-slits  open  into  the  front 
part  of  the  alimentary  canal  called  the  pharynx,  which 
leads  by  a  short  tube,  the  cesopJiagus,  into  the  stomach. 
Note  the  large,  thickened  portion  of  the  alimentary  canal 
leading  from  the  stomach.  This  is  the  pylorus,  and  to  its 
walls  are  attached  a  number  of  finger-like  projections,  the 
pyloric  cceca.  The  pyloric  caeca  secrete  a  fluid  which  is 
poured  into  the  alimentary  canal  and  which  assists  in  the 
process  of  digestion  somewhat  as  does  the  secretion  from 
the  pancreas  of  the  toad.  From  the  pylorus,  passing 
backwards  in  one  or  two  loops,  is  the  small  intestine. 
Trace  this  to  its  exit.  Lying  within  the  mesentery  near 


BRANCH  CHORDATA;   CLASS   PISCES:    THE  FISHES     267 

the   posterior   end  of  the    body-cavity  note  a   small   red 
glandular  mass,  the  spleen. 

At  the  anterior  end  of  the  body  in  front  of  the  liver 
and  between  the  sets  of  gills  note  the  small  pcricardial 
cavity  within  which  is  contained  the  heart.  The  peri- 
cardial  cavity  is  separated  from  the  peritoneal  cavity  by 
a  thick  muscular  wall  against  which  the  liver  abuts.  The 
heart  consists  of  four  parts.  The  posterior  part  is  a  thin- 
walled  reservoir,  the  sinus  venosus,  into  which  blood 
enters  through  the  jugular  vein  from  the  head  and  through 
the  cardinal  vein  from  the  kidney.  From  the  sinus 
venosus  it  passes  forward  into  a  large  chamber,  the 
aiiride.  Next  it  flows  into  the  ventricle,  where,  by  the 
contraction  of  the  walls,  rhythmical  pulsations  force  it  into 
the  conns  arteriosus,  thence  into  the  ventral  aorta,  and 
lastly  into  the  gills,  where  it  is  purified.  After  passing 
through  the  capillaries  in  the  fine  gill-filaments  it  is  again 
collected,  now  pure,  by  paired  arteries  from  each  pair  of 
gills,  which  arteries  unite  to  form  the  dorsal  aorta  ex- 
tending backward  just  below  the  backbone  to  the  end  of 
the  tail.  From  the  dorsal  aorta  a  pair  of  arteries,  the 
subclavian,  are  given  off  to  the  pectoral  fins.  At  this 
point  two  other  arteries  branch  off  ventrally,  the  first  being 
the  cardiac  artery,  which  distributes  blood  to  the  stomach 
and  pyloric  caeca.  The  second  divides  into  several  long 
mesenteric  arteries  supplying  blood  to  all  parts  of  the  in- 
testine and  spleen.  In  the  caudal  region  blood  is  taken 
up  through  the  caudal  vein  and  carried  forward  to  the 
kidneys.  These  strain  out  the  impurities  arising  from 
waste  of  tissues,  after  which  the  blood  is  carried  back  to 
the  sinus  venosus  through  the  cardinal  vein.  From  the 
intestine  it  is  gathered  into  the  large  portal  vein  as  in  the 
toad.  The  portal  vein  carries  blood  to  the  liver,  where 
nutriment  may  be  stored  up,  and  from  thence  it  flows  back 


268  ELEMENTARY  ZOOLOGY 

to  the  sinus  venosus  through  a  very  short  thin-walled 
vessel,  the  hepatic  sinus. 

The  kidneys,  more  or  less  united  in  one  mass,  lie  in  the 
posterior  part  of  the  body-cavity  along  the  dorsal  wall. 
Note  running  from  each  side  of  the  kidney  a  ureter  which 
unites  with  its  fellow  and  opens  into  a  small  urinary 
bladder  which  discharges  through  a  small  opening  im- 
mediately back  of  the  anus. 

The  reproductive  organs  lie  below  the  swim-bladder 
near  the  posterior  end  of  the  body-cavity.  If  the  fish  are 
caught  in  the  spring,  the  greater  part  of  the  body-cavity 
of  the  female  is  found  to  be  filled  with  small  eggs.  When 
mature,  these  eggs  are  deposited  by  the  mother  fish  in  the 
gravel  of  the  stream-bed  where  they  are  fertilized  by  the 
sperm-cells  poured  over  them  by  the  male  and  left  float- 
ing in  the  water. 

The  nervous  system  of  fishes  is  best  studied  in  a  speci- 
men treated  with  nitric  acid.  Carefully  remove  the  roof 
of  the  skull,  thereby  exposing  the  brain.  Most  anteriorly 
make  out,  as  in  the  toad,  the  paired  olfactory  lobes. 
These  are  attached  by  long  stalks  to  the  cerebrum  or 
forebrain,  which  is  followed  by  two  large  hollow  lobes, 
the  midbrain  or  optic  lobes.  Behind  the  midbrain  is  the 
cerebellum.  Following  the  cerebellum  is  the  elongate 
medulla  oblongata,  which  tapers  backward  into  the  spinal 
cord.  How  far  backward  does  the  spinal  cord  extend  ? 
On  each  side  of  the  brain-case  about  opposite  the  cerebel- 
lum are  located  the  auditory  organs,  each  consisting  of 
three  semicircular  canals  which  lie  in  different  planes,  and 
of  the  vestibule.  These  parts  are  filled  with  liquid,  and 
suspended  in  the  liquid  in  the  vestibule  are  small  calcareous 
bodies  called  otoliths  or  ear-stones.  Running  out  beneath 
from  the  midbrain  are  the  optic  nerves,  which  cross,  the 
left  one  connected  with  the  right  eye,  the  right  one  with 
the  left  eye.  From  each  side  of  the  medulla  oblongata 


BRANCH  CHORD  AT /I;   CLASS  PISCES:    THE  FISHES     269 

there  is  given  off  a  large  nerve,  the  vagus,  which  sends 
branches  to  the  lateral  line  organs  on  either  side,  and 
extends  backward  to  the  stomach  and  viscera. 

For  further  study  of  the  nervous  system  see  Parker's 
'  •  Zootomy, ' '  pp.  1 2  2-1 30. 

Make  a  drawing  of  the  nervous  system  as  worked  out. 

TECHNICAL  NOTE. — To  make  a  good  skeleton  immerse  a  fresh 
or  preserved  specimen  for  some  time  in  a  hot  soap  solution.  When 
the  muscles  have  commenced  to  soften  remove  the  body  from  the 
solution,  pick  the  flesh  away,  and  leave  to  dry. 

Note  that  the  main  axis  of  the  skeleton  is  composed  of 
vertebra  placed  end  to  end.  How  many  vertebrae  are 
there  ?  What  vertebra:  bear  ribs  f  The  ribless  ones 
beyond  the  body-cavity  are  called  caudal  vertebra.  Note 
the  inter  spinal  bones  which  support  the  fins,  with  large 
muscles  on  either  side  to  control  their  action.  Note  that 
the  group  of  bones  supporting  the  pectoral  fin  is  attached 
to  the  back  of  the  brain -case  and  makes  up  the  shoulder 
girdle.  The  ventral  fins  are  attached  to  a  rudimentary 
pelvic  girdle^  attached  in  front  to  the  shoulder  girdle,  as 
the  shoulder  girdle  is  in  turn  attached  to  the  skull.  It 
will  be  seen  that  the  sunfish  has  no  neck  and  we  may  say, 
also,  no  back.  Its  skeleton  consists  only  of  a  tail  attached 
to  the  skull.  The  brain-case  is  made  up  of  a  number  of 
bones  closely  joined  together.  From  it  is  suspended  the 
lower  jaw,  which  comprises  a  number  of  bones  but  loosely 
attached  to  each  other.  Overlying  these  is  the  system 
of  membrane  bones  already  mentioned,  including  the 
opercle  or  gill-cover. 

For  a  detailed  study  of  the  fish-skeleton  see  Parker's 
"Zootomy,"  pp.  86-101,  or  Parker  and  Hasvvell's 
4  *  Zoology, "  vol.  II.  pp.  183-195. 

Life-history  and  habits. — The  sunfish  or  4<  pumpkin- 
seed"  lives  in  quiet  corners  of  the  brooks  and  rivers, 
preferably  under  a  log  or  at  the  root  of  an  old  stump.  It 


270  ELEMENTARY  ZOOLOGY 

is  a  beautiful  fish,  shining  "like  a  coin  fresh  from  the 
mint."  Its  body  is  mottled  golden,  orange  and  blue, 
with  metallic  lustre,  darker  above,  pale  or  yellowish 
below.  Its  fins  are  of  the  same  color.  The  tip  of  its 
opercle  is  prolonged  like  an  ear  and  jet  black  in  color, 
with  a  dash  of  bright  scarlet  along  its  lower  edge.  Nearly 
all  the  thirty  species  of  sunfish  found  in  the  United  States 
have  this  black  ear,  but  some  have  it  long,  some  short, 
and  in  some  it  is  trimmed  with  yellow  or  blue  instead  of 
scarlet. 

The  sunfish  lays  its  eggs  in  the  spring  in  a  rude  nest  it 
scoops  in  the  gravel,  over  which  it  stands  guard  with  its 
bright  fins  spread,  looking  as  big  and  dangerous  as 
possible.  When  thus  employed  it  takes  the  hook  savagely, 
perhaps  regarding  the  worm  as  a  dangerous  enemy.  The 
young  fishes  soon  hatch,  looking  very  much  like  their 
parents,  although  more  transparent  and  not  so  brightly 
colored.  They  grow  rapidly,  feeding  on  insects  and 
other  small  creatures,  and  reach  their  growth  in  two  or 
three  years.  They  do  not  wander  far  and  never  willingly 
migrate.  Students  should  verify  this  account  on  the 
different  species.  A  more  exact  study  of  the  nests  of  the 
different  species  and  the  fishes'  defence  of  them  would  be 
a  valuable  addition  to  our  knowledge.  The  most  striking 
traits  of  the  habits  of  this  fish  are  its  vivacity  and  courage ; 
it  reveals  its  great  muscular  strength  when  captured. 
The  sexes  are  similar  in  appearance  and  both  defend  the 
nest  alike. 

OTHER    FISHES. 

Fishes  constitute  the  largest  class  of  vertebrate  animals 
and  are  to  be  found  eveTywhereFTn ponds,  streams,  or 
ocean.  About  15,000  species  offish  are  known,  of  which 
3,000  live  in  North  America.  Thejargest  ofjil^  fishes  is 
the  basking  shark  (Cetorhinus),  which- reaches  a  length 


lateral  line 
opercular  flap  \ 


gill-rakers 

i 

gall  bladder      I 
1 


nostrils 


pericardia!  cavity 


I    ventricle 
conus  arteriosub 


ventral  fin 


intestine 


body  cavity 


FIG.  112. — Dissection 


fin  ^       /  Cat7%  °f  ^e  swim-bladder 
^-  ,  X  kidney 


"un-nary  bladder 
'  opening  from  kidneys 


body  muscles 


fthe  sunfisli,  Apomotis  sp. 


BRANCH  CHORD  AT  A ;   CLASS  PISCES:    THE  FISHES      271 

of  thirty-six  feet.  The  smallest  is  the  dwarf  goby 
i .  1  /is  tic  I i  thys  )7~te  s  s  than  half  an  inch  long,  found  in  Luzon, 
one  of  the  Philippine  Islands.  Between  these  extremes 
is  every  variety  in  size,  form,  and  relative  proportions. 
The  body,  for  example,  may  be  greatly  elongated  and 
almost  cylindrical  as  in  the  eels;  or  long  and  flattened 
from  side  to  side  as  in  the  ribbon-fishes;  or  the  head  may 
be  very  large,  wider  and  higher  than  the  rest  of  the  body 
as  in  the  anglers,  or  may  have  a  great  beak  as  in  the 
sword-fish. 

Body  form  and  structure. — When  we  consider  the  fish 
as  a  whole,  we  find  first  a  body  formed  for  progression  in 
the  water,  the  typical  fish  being  pointed  at  each  end  (the 
shorter  point  in  front),  and  having  the  sides  flattened,  the 
back  and  belly  rather  narrow,  and  the  motive  power 
located  in  the  fin  on  the  tail.  From  this  typical  form 
diverge  all  conceivable  variations,  adaptations  to  every 
sort  offish  life. 

Most  fishes  have  the  body  covered  with  seal  eg,  although 
many  have  the  skin  naked  or  covered  with  small  scales 
so  hidden  in  the  skin  as  to  be  hardly  visible.  The  scales 
are  small  horny  or  bony  plates  which  fit  into  small  pockets 
or  folds  of  the  skin,  and  are  usually  arranged  shingle- 
fashion,  overlapping  each  other.  They  are  of  various 
shapes,  mostly  classified  as  of  three  kinds,  namely,  squarish 
enamelled  scales  called  ganoid,  roundish  smooth-edged 
called  cycloid,  and  roundish  tooth-edged  called  ctenoid. 

The  skeleton  of  the  fish  is  relatively  complex.  Its 
bones  are  comparatively  soft,  having  little  lime  in  them, 
indeed  in  many  cases  they  are  mere  cartilage.  The 
vertebral  column  is  made  of  twenty-four  vertebrae  in  the 
typical  fishes,  the  number  in  the  others  being  variously 
increased,  or  sometimes  diminished.  These  vertebrae  are 
of  two  classes,  abdominal  or  body,  and  caudal  or  tail 
vertebrae.  The  former  have  a  neural  arch  which  encloses 


272  ELEMENTARY  ZOOLOGY 

the  spinal  cord  and  from  which  projects  a  spine.  Below, 
the  processes  spread  apart,  surrounding  the  kidneys  and 
partly  enclosing  the  air-bladder.  To  these  processes  ribs 
are  loosely  attached.  The  caudal  vertebrae  have  no  ribs 
and  leave  no  room  below  for  viscera.  Their  lower  arch 
(hsemal),  similar  to  the  dorsal  (neural)  arch,  surrounds  a 
blood-vessel.  The  fins  of  a  fish  are  composed  of  bony 
rods  or  rays  joined  by  membrane.  Some  of  these  rays 
may  be  unbranched  and  unjointed,  being  then  known  as 
spines,  and  usually  occupy  the  front  part  of  the  fin. 
Other  rays  are  made  up  of  little  joints  and  are  usually 
branched  toward  their  tip.  Such  ones  are  called  soft 
rays.  Soft  rays  make  up  the  greatest  part  of  most  fins. 
The  vertical  fins  are  on  the  middle  line  of  the  body. 
These  are  the  dorsal  above,  anal  below,  and  caudal  form- 
ing the  end  of  the  tail.  The  paired  pectoral  and  ventral 
fins  are  ranged  one  on  each  side  corresponding  to  the 
arms  and  legs  of  higher  animals.  The  pectoral  fin  or 
arm  is  fastened  to  a  series  of  bones  called  the  shoulder 
girdle.  These  bones  do  not  correspond  to  those  in  the 
shoulder  girdle  of  the  higher  animals,  and  the  various 
parts  in  the  two  structures  are  differently  named.  The 
uppermost  bone  of  the  shoulder  girdle  is  usually  attached 
to  the  skull.  To  the  lowermost  is  attached  the  rudimen- 
tary pelvis,  which  supports  the  hinder  limb  or  ventral  fin. 
Usually  the  pelvis  is  farther  back  and  loose  in  the  flesh, 
but  sometimes  it  is  placed  far  forward,  being  occasionally 
attached  at  the  chin. 

The  head  contains  the  various  bones  of  the  cranium, 
usually  closely  wedged  together  and  not  easily  distin- 
guished. The  jaws  are  each  made  of  several  pieces ;  the 
lower  one  is  suspended  from  the  skull  by  a  chain  of  three 
flat  bones.  The  jaws  may  bear  any  one  of  a  great  variety 
of  forms  of  teeth  or  no  teeth  at  all,  and  any  of  the  bones 
of  the  mouth-cavity  and  throat  may  have  teeth  as  well. 


BRANCH   CHORD  AT  A;   CLASS  PISCES:    THE  HSHES    ?73 

On  the  outside  of  the  head  are  numerous  bones  called 
membrane  bones,  because  they  are  made  up  of  ossified 
membrane.  The  most  important  of  these  is  the  operclc 
or  gill-cover.  Within  are  the  tongue  with  the  fivejjill- 
arches  attached  to  it  below  and  to  the  floor  of  the  skull 
a5ove~  the  last  arch  being  usually  modified  to  form  the 
pharyngeal  jaw. 

The^stomach  may  be  a  blind  sac  with  entrance  and  exit 
close  together,  or  it  may  have  the  form  of  a  tube  or 
siphon.  At  its  end  are  often  found  the  large  glandular 
tubes  called  pyloric  caeca  which  secrete  a  digestive  fluid ; 
and  to  its  right  side  is  attached  the  red  spleen.  Theliver 
is  large,  having  usually,  but  not  always,  a  gall-bladder; 
it  "pouTs  its  secretion  into  the  upper  intestine.  In  fishes 
which  feed  on  plants  the  intestine  is  long,  but  it  is  short 
in  those  which  eat  flesh,  because  flesh  is  digested  in  the 
stomach,  not  in  the  intestines.  The  kidney  is  usually  a 
long  slender  forked  gland  showing  little  variation.  The 
egg-glands  differ  greatly  in  different  sorts  of  fishes,  the  size 
and  number  of  eggs  varying  equally.  The  air-bladder  is 
a  lung  which  has  lost  both  lung  structure  and  respiratory 
function,  being  simply  a  sac  filled  with  gas  secreted  from 
the  blood,  and  lying  in  the  upper  part  of  the  abdominal 
cavity.  It  is  subject  to  many  variations.  In  the  gar 
pike,  bow-fin  and  the  lung-fishes  of  the  tropics,  the  air- 
bladder  is  a  true  lung  used  for  breathing  and  connected 
by  a  sort  of  glottis  with  the  oesophagus.  In  others  it  is 
rudimentary  or  even  wholly  wanting,  while  in  still  others 
its  function  as  an  air-sac  is  especially  pronounced,  and  in 
many  it  is  joined  through  the  modified  bones  of  the  neck 
to  the  organ  of  hearing. 

The  blood  of  the  fish  is  purified  by  circulation  through 
its  gills.  These  are  a  series  of  slender  filaments  attached 
to  bony  arches.  Among  them  the  blood  flows  in  and  out, 
coming  in  contact  with  the  water  which  the  fish  takes  in 


274  ELEMENTARY  ZOOLOGY 

through  its  mouth  and  which  passes  across  the  gills  to  be 
expelled  through  the  gill-openings.  The  blood  is  received 
from  the  body  into  the  first  chamber  of  the  heart,  a  mus- 
cular sac  called  the  auricle.  From  here  it  passes  into  the 
ventricle,  a  chamber  with  thicker  walls,  the  contraction 
of  which  sends  it  to  the  gills,  thence  without  return  to  the 
heart  it  passes  over  the  body.  The  circulation  of  blood 
in  fishes  is  slow,  and  the  blood,  which  receives  relatively 
little  oxygen,  is  cold,  being  but  little  warmer  than  the 
water  in  which  the  individual  fish  lives. 

Inside  the  cranium  or  brain-case  is  the  brain,  small  and 
composed  of  ganglia  which  are  smooth  at  the  surface  and 
contain  little  gray  matter.  At  the  posterior  end  of  the 
brain  is  the  thickened  end  of  the  spinal  cord,  called  the 
medulla  oblongata.  Next  overlapping  this  is  the  cere- 
bellum, always  single.  Before  this  lie  the  largest  pair  of 
ganglia,  the  optic  lobes  or  midbrain,  round,  smooth,  and 
hollow.  From  the  under  side  of  these,  nerves  run  to  the 
eyes  with  or  without  a  chiasma  or  crossing.  In  front  of 
the  optic  lobes  and  smaller  than  them  is  the  cerebrum  or 
forebrain,  usually  of  two  ganglia  but  sometimes  (in  the 
sharks)  united  into  one.  In  front  of  these  are  the  small 
olfactory  lobes  which  send  nerves  to  the  nostrils. 

The  sense  organs  are  well  developed.  The  sense  of 
touch  has  in  some  fishes  special  organs  for  its  better 
effectiveness.  For  instance  certain  fin-rays  in  some 
fishes,  or,  as  in  the  catfish,  slender,  fleshy,  whip-like 
processes  on  the  head,  are  developed  as  feelers  or  special 
tactile  organs.  Other  fishes,  the  sucker  and  loach  for 
example,  have  specially  sensitive  lips  and  noses  with 
which  they  explore  their  surroundings.  The  sense  of 
taste  does  not  seem  to  be  well  developed  in  this  group. 
Taste-papillae  are  often  present  in  small  numbers  on  the 
tongue  or  on  the  palate.  The  sense  of  smell  is  good. 
The  olfactory  organs,  one  on  each  side  of  the  head,  are 


BRANCH  CHORD  AT  A;  CLASS  PISCES:   THE  FISHES    275 


hollow  sac-like  depressions,  closed  at  the  rear.  In 
cases  each  sac  has  two  openings  or  nostrils.  The  sense 
oj"  hearing  is  not  very  keen.  The  ears  are  fluid-filled  sacs 
buried  in  the  skull,  and  without  external  or  (except  in  a 
few  cases)  internal  opening.  Fishes  are  far  more  sensi- 
tive to  sudden  jars  or  sudden  movements  than  to  any 
sound.  They  possess  what  is  generally  believed  to  be  a 
special  sense  organ  not  found  in  other  animals.  This  is 
the  lateral  line  which  extends  along  the  sides  of  the  body 
and  which  consists  of  a  series  of  modified  scales  (each  one 
with  a  mucous  channel)  richly  supplied  with  nerves.  The 
eyes  jire  usually  large  and  conspicuous.  They  differ 
mainly  from  the  eyes  of  other  vertebrates  in  their  myopic 
spherical  crystalline  lens,  made  necessary  by  the  density 
of  the  medium  in  which  fishes  live.  There  are  usually  no 
eyelids,  the  skin  of  the  body  being  continuous  but  trans- 
parent over  the  eyes.  Being  near-sighted,  fishes  do  not 
discriminate  readily  among  forms,  their  special  senses 
fitting  them  in  general  to  distinguish  motions  of  their 
enemies  or  prey  rather  than  to  ascertain  exactly  the 
nature  of  particular  things. 

The  colors  of  fishes  are  in  general  appearance  protec- 
tive. Thus  most  individuals  are  white  on  the  belly, 
mimicking  the  color  of  the  sky  to  the  enemy  which 
pursues  them  from  below.  Seen  from  above  most  of  them 
are  greenish,  like  the  water,  or  brownish  gray  and 
mottled,  like  the  bottom.  Those  thaf  live  on  sand  are 
sand-colored,  those  on  lava  black,  and  those  among  rose- 
red  sea-weeds  bright  red.  In  many  cases,  especially 
among  kinds  that  are  protected  by  their  activity,  brilliant 
colors  and  showy  markings  are  developed.  This  is 
especially  true  among  fishes  of  the  coral  reefs,  though 
species  scarcely  less  brilliant  are  found  among  the  darters 
of  our  American  brooks. 

Among    fresh-water    fishes    bright    colors,     crimson, 


276  ELEMENTARY  ZOOLOGY 

scarlet,  blue,  creamy  white,  are  developed  in  the  breeding 
season,  the  then  vigorous  males  being  the  most  highly 
colored.  Many  of  the  feeble  minnows  even  become  very 
brilliant  in  the  nuptial  season  of  May  and  June.  Color  in 
fishes  is  formed  by  minute  oil-sacs  on  the  scales,  and  it 
often  changes  quickly  with  changes  in  the  nervous  condi- 
tion of  the  individuals. 

Development  and  life-history. — The  breeding  habits 
of  fishes  are  extremely  varied.  Most  fishes  do  not  pair, 
but  in  some  cases  pairing  takes  place  as  among  higher 
animals.  Ordinarily  fishes  lay  their  eggs  on  the  bottom  in 
shallow  water,  either  in  brooks,  lakes,  or  in  the  sea.  The 
eggs  of  fishes  are  commonly  called  spawn,  and  egg-laying 
is  referred  to  as  spawning.  The  spawn  of  some  fishes  is 
esteemed  a  special  food  delicacy.  Spring  is  the  usual  time 
of  spawning,  though  some  fishes  spawn  in  summer  and 
some  even  in  winter;  generally  they  move  from  their  usual 
haunts  for  the  purpose.  The  eggs  of  the  different  species 
vary  much  in  size,  ranging  from  an  inch  and  a  half  in 
diameter  (barn-door  skate)  down  to  the  tiniest  dots,  like 
those  of  the  herring.  The  number  of  eggs  laid  also  varies 
greatly.  The  trout  lays  from  500  to  i  ,000,  the  salmon 
about  10,000,  the  herring  30,000  to  40,000,  and  some 
species  of  river  fish  500,000,  while  certain  flounders, 
sturgeons,  and  others  each  lay  several  millions  of  eggs. 
The  adults  rarely  pay  any  attention  to  the  eggs,  which  are 
hatched  directly  by  the  heat  of  the  sun  or  by  heat  absorbed 
from  the  water.  The  length  of  incubation  varies  much. 
When  the  young  fish  leaves  the  egg-shell  it  carries,  in  the 
case  of  most  species,  a  part  of  the  yolk  still  hanging  to 
its  body.  Its  eyes  are  very  large,  and  its  fins  are  repre- 
sented by  thin  strips  of  membrane.  It  usually  undergoes 
no  great  changes  in  development  from  the  first,  resembling 
the  adult  except  in  size.  But  some  of  the  ocean  fishes 


BRANCH  CHORD  AT  A  i  CLASS  PISCES:   THE  FISHES    277 

show  a  metamorphosis  almost  as  striking  as  that  of  insects 
or  toads  or  frogs. 

Some  fishes  build  nests.  Sticklebacks  build  elaborate 
nests  in  the  brooks  and  defend  them  with  spirit.  Sun- 
fishes  do  the  same,  but  the  nests  are  clumsier  and  not 
so  well  cared  for. 

The  salmon  is  the  type  of  fishes  which  run  up  from  the 
sea  to  lay  their  eggs  in  fresh  water.  The  king  salmon  of 
the  Columbia  River,  for  example,  leaves  the  sea  in  the 
high  waters  of  March  and  ascends  without  feeding  for  over 
a  thousand  miles,  depositing  its  spawn  in  some  small 
brook  in  the  fall.  After  making  this  long  journey  to  lay 
the  eggs,  the  salmon  become  much  exhausted,  battered 
and  worn,  and  are  often  attacked  by  parasitic  fungi.  They 
soon  die,  probably  none  ofthem  ever  surviving  to  lay  eggs 
a  second  time. 

Classification. — A  fish  is  an  aquatic  vertebrate,  fitted 
to  breathe  the  air  contained  in  water,  and  never  develop- 
ing fingers  and  toes.  Accepting  this  broad  general 
definition  we  find  at  once  that  there  are  very  great  differ- 
ences among  fishes.  Some  differ  more  from  others  than 
the  ordinary  forms  differ  from  rabbits  or  birds.  So 
although  we  have  entitled  this  chapter  as  if  all  fishes 
belonged  to  the  class  Pisces,  we  cannot  arrange  them 
satisfactorily  in  less  than  three  classes. 

The  lancelets  (Leptocardii). — The  lowest  class  of  fish- 
like  animals  is  that  of  the  lancelets,  the  Leptocardii. 
These  little  creatures,  translucent,  buried  in  the  sand,  of 
the  size  and  form  of  a  small  toothpick,  are  fishes  reduced 
to  their  lowest  terms.  They  have  the  form,  life,  and  ways 
of  a  fish,  but  no  differentiated  skull,  brain,  heart,  or  eyes. 
Moreover  they  have  no  limbs,  no  jaws,  no  teeth,  no 
scales.  The  few  parts  they  do  have  are  arranged  as  in  a 
fish,  and  they  show  something  in  common  with  the  fish 


278  ELEMENTARY  ZOOLOGY 

embryo.  Lacking  a  distinct  head,  the  lancelets  are  put 
by  some  zoologists  in  a  group  called  the  Acrania,  as 
opposed  to  the  Craniata,  which  includes  all  the  other 
vertebrates.  Lancelets  have  been  found  in  the  North 
Atlantic  and  Mediterranean,  on  the  west  coast  of  North 
America,  on  the  east  coast  of  South  America  and  on  the 
coasts  of  Japan,  Australia,  New  Zealand,  the  East  Indies 
and  Malayan  Islands.  The  best-known  members  of  the 
group  belong  to  the  genus  Amphioxiis.  There  are  but 
one  to  two  other  genera  in  the  class. 

The  lampreys  and  hag-fishes  (Cyclostomata). — The 
next  class  of  fish-like  animals  is  that  of  the  lampreys  (fig. 


FlG.  113. — A  lamprey,  Petromvzon  martnus.     (After  Goode.) 

113)  and  hag-fishes,  the  Cyclostomata.  The  lampreys 
and  hags  are  easily  distinguished  from  the  true  fishes  by 
their  sucking  mouth  without  jaws,  their  single  median 
nostril,  tHeir  eel-like  shape  and  lack  of  lateral  appendages 
or  paired  fins.  The  hag-fishes  (Myxine),  which  are 
marine,  attach  themselves  by  means  of  a  sucker-like  mouth 
to  living  fishes  (the  cod  particularly),  gradually  scraping 
and  eating  their  way  into  the  abdominal  cavity  of  the  fish. 
These  hags  or  "borers  "  "approach  most  nearly  to  the 
condition  of  an  internal  parasite  of  any  vertebrate. ' '  The 
lampreys,  or  lamprey-eels  as  they  are  often  called  because 
of  their  superficial  resemblance  to  true  eels,  are  both 
marine  and  fresh-water  in  their  habitat,  and  most  of  them 
attach  themselves  to  live  fishes  and  suck  their  blood. 
They  also  feed  on  Crustacea,  insects,  and  worms.  The 


BRANCH  CHORD  AT  A;  CLASS  F>1$CES :   THE  PISHES 

brook -lamprey,  Lampetra  wilder! ,  is  never  parasitic.  It 
reaches  its  full  size  in  larval  life  and  transforms  simply 
for  spawning.  The  sea-  and  lake-lampreys  ascend  small 
fresh-water  streams  when  ready  to  lay  their  eggs,  few 
living  to  return.  Sometimes  small  piles  of  stones  are 
made  for  nests.  The  young  undergo  a  considerable 
metamorphosis  in  their  development.  The  largest  sea- 
lampreys  reach  a  length  of  three  feet.  The  common 
brook-lampreys  are  from  eight  to  twelve  inches  long  only. 

The  true  fishes  (Pisces). — All  the  other  fish-like  ani- 
mals are  grouped  in  the  class  Pisces.  They  are  charac- 
terized, when  compared  with  the  lower  fish-like  forms  just 
referred  to,  by  the  presence  of  jaws,  shoulder  girdle,  and 
pelvic  girdle.  The  class^includes  both  the  cartilaginous 
and  bony  fishes,  and  is  divided  into  three  sub-classes, 
namely,  the  Elasmobranchii,  including  the  sharks,  rays, 
skates,  torpedoes,  etc.,  the  Holocephali,  including  the 
chimaeras  (a  few  strange-bodied  forms),  and  the  Teleos- 
tomi,  including  all  the  other  fishes,  as  the  trout,  catfishes, 
darters,  bass,  herring,  cod,  mackerel,  sturgeons,  etc.,  etc. 

The  sharks,  skates,  etc.  (Elasmobranchii). --The 
sharks  and  skates  are  characterized  by  the  possession  of 
a  skeleton  composed  of  cartilage  and  not  bone,  as  in 
the  bony  fishes;  they  have  no  operculum;  their  teeth 
are  distinct,  often  large  and  highly  specialized,  and  their 
eggs  are  few  and  very  large.  There  are  two  principal 
groups  among  Elasmobranchii,  viz.,  the  sharks,  which 
usually  have  an  elongate  body,  and  always  have  the  gill- 
openings  on  the  sides,  and  the  rays  or  skates,  which  have  a 
broad  flattened  body  with  the  gill-openings  always  on  the 
under  side.  All  the  members  of  both  groups  are  marine. 
The  sharks  are  active,  fierce,  usually  large  fishes,  which 
live  in  the  surface-waters  of  the  ocean  and  make  war  on 
other  marine  animals,  all  of  the  species  except  half  a 
dozen  being  fish-caters.  The  shark's  mouth  is  on  the. 


2&o  .     ELEMENT  A  kY  ZOOLOGY 

under  side  of  the  usually  conical  head,  and  the  animal 
often  turns  over  on  its  back  in  order  to  seize  its  prey. 
The  largest  American  sharks,  and  the  largest  of  all  fishes, 
are  the  great  basking-sharks  (CctorJiinus},  which  reach  a 
length  of  nearly  forty  feet.  They  get  their  name  from 
their  habit  of  gathering  in  numbers  and  floating  motion- 
less on  the  surface.  They  feed  chiefly  on  fishes. 

The  hammer-headed  sharks  (Sphyrna]  are  odd  sharks 
which  have  the  head  mallet  or  kidney  shaped,  twice  as  wide 
as  long,  the  eyes  being  situated  on  the  ends  of  the  lateral 
expansions  of  the  head.  The  man-eating  or  great  white 
sharks  (Carcharodon)  are  nearly  as  large  as  the  basking- 
sharks,  and  are  extremely  voracious.  They  will  follow 
ships  for  long  distances  for  the  refuse  thrown  overboard. 
They  do  not  hesitate  to  attack  man.  Among  the  more 
familiar  smaller  sharks  are  the  dog-fishes  and  sand-sharks 
of  our  Atlantic  coast. 

The  rays  and  skates  are  also  carnivorous,  but  are  with 
few  exceptions  sluggish,  lying  at  the  bottom  of  shallow 
shore-waters.  They  feed  on  crabs,  molluscs,  and  bottom- 
fishes.  The  small  common  skates,  /'tobacco-boxes" 
(Raja  erinaced]  (fig.  114),  about  twenty  inches  long,  and 
the  larger  "barn-door  skates"  (R.  hcvis),  are  numer- 
ous along  the  Atlantic  coast  from  Virginia  northward. 
Especially  interesting  members  of  this  group,  because  of 
the  peculiar  character  of  the  injuries  produced  by  them, 
are  the  sting-rays  and  torpedoes  or  electric-rays.  The 
sting-rays  (Dasyatis)  have  spines  near  the  base  of  the  tail 
which  cause  very  painful  wounds.  The  torpedoes  (Narcine) 
have  two  large  electrical  organs,  one  on  each  side  of  the 
body  just  behind  the  head,  with  which  they  can  give  a 
strong  electric  shock.  "The  discharge  from  a  large  in- 
dividual is  sufficient  to  temporarily  disable  a  man,  and 
were  these  animals  at  all  numerous  they  would  prove 
dangerous  to  bathers. ' '  Very  different  from  the  typical 


BRANCH  CHORD  AT  A;   CLASS  PISCES:   THE  FISHES    281 

rays  in  external  appearance  are  the  saw-fishes  ( Pristis 
pcctinatis),  which  belong  to  this  group.  The  body  is 
elongate  and  shark-like,  and  has  a  long  sa\v-like  snout. 
This  sa\v,  which  in  large  individuals  may  reach  a  length 
of  six  feet  and  a  breadth  of  twelve  inches,  makes  its 
owner  formidable  among  the  small  sardines  and  herring- 


FIG.  114. — The  common  skate,  Raja  erinacea.     (From  Kingsley.) 

like  fishes  on  which  it  feeds.    The  saw-fishes  live  in  tropi- 
cal rivers,  descending  to  the  sea. 

The  bony  fishes  (Teleostomi). — The  bony  or  true  fishes 
are  distinguished  from  the  lampreys  and  sharks  and  rays 
by  having  in  general  the  skeleton  bony,  not  cartilaginous, 
the  skull  provided  with  membrane  bones,  and  the  eggs 
small  and  many.  In  this  group  are  included  all  the 
fishes  of  our  fresh- water  lakes,  ponds,  and  streams  as  well 
as  most  of  the  marine  forms.  Fish  life,  being  spent  under 


2&2  .       ELEMENTARY  ZOOLOGY 

water,  is  not  familiar  to  most  of  us,  and  beginning  students 
are  rarely  helped  enough  in  getting  acquainted  with  the 
different  kinds  and  the  interesting  habits  of  fishes.  But 
they  offer  a  field  of  study  which  is  really  of  unusual  interest 
and  profit.  We  can  refer  in  the  following  paragraphs  to 
but  few  of  the  numerous  common  and  readily  found  kinds, 
and  to  these  but  briefly. 

Closely  related  to  the  sunfish,  studied  as  example  of 
the  bony  fishes,  are  the  various  kinds  of  bass,  as  the 
"crappie  "  (Pomoxis  annularis),  the  calico  bass  (P.  sepa- 
roidcs),  the  rock-bass  (Ambloplitcs  rupcstris)  and  the 
large-mouthed  and  small-mouthed  black  bass  (Micropterus 
salmoides  and  M.  dolomieu  respectively).  All  the  mem- 
bers of  this  sunfish  and  bass  family  are  carnivorous  fishes 
especially  characteristic  of  the  Mississippi  valley. 

Another  family  of  many  species  especially  common  in 
the  clear,  swift,  and  strong  Eastern  rivers  is  that  of  the 
darters  and  perches.  The  darters  are  little  slender-bodied 
fishes  which  lie  motionless  on  the  bottom,  moving  like  a 
flash  when  disturbed  and  slipping  under  stones  out  of  sight 
of  their  enemies.  Some  are  most  brilliantly  colored,  sur- 
passing in  this  respect  all  other  fresh-water  fishes. 

Unlike  the  sunfishes  and  darters  are  the  catfishes, 
composing  a  great  family,  the  Siluridae.  The  catfish 
(Ameturus)  gets  its  name  from  the  long  feelers  about  its 
mouth ;  from  these  feelers  also  come  its  other  names  of 
horned  pout,  or  bull-head.  It  has  no  scales,  but  its  spines 
are  sharp  and  often  barbed  or  jagged  and  capable  of  mak- 
ing a  severe  wound. 

Remotely  allied  to  the  catfish  are  the  suckers,  min- 
nows, and  chubs,  with  smooth  scales,  soft  fins  and  soft 
bodies  and  the  flesh  full  of  small  bones.  These  little  fish 
are  very  numerous  in  species,  some  kinds  swarming  in 
all  fresh  water  in  America,  Europe,  and  Asia.  They 
usually  swim  in  the  open  water,  the  prey  of  every  carniv- 


BRANCH  CHORDATA;   CLASS  PISCES:   THE  FISHES     283 

orous  fish,  making  up  by  their  fecundity  and  their  insig- 
nificance for  their  lack  of  defensive  armature.  In  some 
species  the  male  is  adorned  in  the  spring  with  bright 
pigment,  red,  black,  blue,  or  milk-white.  In  some  cases, 
too,  it  has  bony  warts  or  horns  on  its  head  or  body.  Such 
forms  are  known  to  the  boys  as  horned  dace. 

Most  interesting   to  the   angler   are   the  fishes  of  the 
salmon  and  trout  (fig.  115)  family,  because  they  are  gamy, 


FIG.  115. — The  rainbow-trout,  Salmo  iri..ens.     (From  specimen.) 

beautiful,  excellent  as  food  and  above  all  perhaps  because 
they  live  in  the  swiftest  and  clearest  waters  in  the  most 
charming  forests.  The  salmon  live  in  the  ocean  most  of 
their  life,  but  ascend  the  rivers  from  the  sea  to  deposit 
their  eggs.  The  king  salmon  (Oncorhynchus  tschawy- 
tscha)  of  the  Columbia  goes  up  the  great  river  more  than 
a  thousand  miles,  taking  the  whole  summer  for  it,  and 
never  feeding  while  in  fresh  water.  .  Besides  the  different 
kinds  of  salmon,  the  black-spotted  or  true  trout,  the  charr 
or  red-spotted  trout  of  various  species,  the  whitefish 
(Coregonus),  the  grayling  ( Thymallus  signifer)  and  the 
famous  ayu  of  Japan  belong  to  this  family. 

In  the  sea  are  multitudes  of  fish  forms  arranged  in  many 
families.  The  myriad  species  of  eels  agree  in  having  no 
ventral  fins  and  in  having  the  long  flexible  body  of  the 
snake.  Most  of  them  live  in  the  sea,  but  the  single 


284  ELEMENTARY  ZOOLOGY 

genus  (Anguilla]  or  true  eel  which  ascends  the  rivers  is 
exceedingly  abundant  and  widely  distributed.  Most  eels 
are  extremely  voracious,  but  some  of  them  have  mouths 
that  would  barely  admit  a  pin-head.  The  codfish  (Gadus 
callarias)  is  a  creature  of  little  beauty  but  of  great  useful- 
ness, swarming  in  all  arctic  and  subarctic  seas.  The 


FIG.  116. — The  winter  flounder,  Pseudopleuronectes  americanus. 
(After  Goode. ) 

herring  (Clupea  Jiarengiis]^  soft  and  weak  in  body,  are 
more  numerous  in  individuals  than  any  other  fishes.  The 
flounders  (fig.  116)  of  many  kinds  lie  flat  on  the  sea- 
bottom.  They  have  the  head  so  twisted  that  the  two 
eyes  occur  both  together  on  the  uppermost  side.  The 
members  of  the  great  mackerel  tribe  swim  in  the  open 
sea,  often  in  great  schools.  Largest  and  swiftest  of  these 
is  the  sword-fish  (Xipliias  gladius),  in  which  the  whole 
upper  jaw  is  grown  together  to  form  a  long  bony  sword, 
a  weapon  of  offence  that  can  pierce  the  wooden  bottom 
of  a  boat. 

Many  of  the  ocean  fishes  are  of  strange  form  and  ap- 
pearance. The  sea-horses  (Hippocampus  sp.)  (fig.  117) 
are  odd  fishes  covered  with  a  bony  shell  and  with  the 
head  having  the  physiognomy  of  that  of  a  horse.  They 
are  little  fishes  rarely  a  foot  long,  and  cling  by  their 


BRANCH  CHORD  AT  A;  CLASS  PISCES:  THE  FISHES      285 


curved   tails   to   floating   seaweed.       The    pipefish    (Syn- 

£nat/uis  fnsanti)  is  a  sea-horse  straightened  out.      The 

porcupine-fishes  and  swellfishes  (Tctraodontidce)  have  the 

power    of    filling    the    stomach 

with    air  which  they  gulp  from 

the  surface.      They  then  escape 

from    their  pursuers  by  floating 

as   a   round   spiny   ball    on    the 

surface.     The  flying-fishes  (Exo- 

ccetns)  leap  out  of  the  water  and 

sail   for   long  distances   through 

the  air,  like  grasshoppers.    They 

cannot  flap  their   long   pectoral 

fins     and     do     not     truly     fly; 

nevertheless  they  move   swiftly 

through  the  air  and  thus  escape 

their  pursuers.      In  its  structure 

a  flying-fish  differs  little  from  a 

pike  or  other  ordinary  fish. 

Foi  an  account  of  the  fishes 
of  North  America  see  Jor- 
dan's "Manual  of  Vertebrates,  " 
eighth  edition,  '  pp.  5-173  .  and 
Jordan  and  Kvermann's  -  Fishes 
of  North  and  Middle  America," 
where  the  3,127  species  known  from  our  continent  are 
described  in  detail  with  illustrative  figures. 

Habits  and  adaptations.—  The  chief  part  of  a  fish's  life 
is  devoted  to  eating,  and  as  most  fishes  feed  on  other 
fishes,  all  are  equally  considerably  occupied  in  providing 
for  their  own  escape. 

In  general  the  provisions  for  seizing  prey  are  confined 
to  sharp  teeth  and  the  strong  muscles  which  propel  the 
caudal  fin.  But  in  some  cases  special  contrivances 
appear.  In  one  large  group  known  collectively  as  the 


Goode.) 


2 86  ELEMENTARY  ZOOLOGY 

"  anglers  "  the  first  spine  of  the  dorsal  fin  hangs  over  the 
mouth.  It  has  at  its  tip  a  fleshy  appendage  which  serves 
as  a  bait.  Little  fishes  nibble  at  this,  the  mouth  opens, 
and  they  are  gone.  In  the  deep  seas,  many  fishes  are 
provided  with  phosphorescent  spots  or  lanterns  which 
light  up  the  dark  waters,  and  enable  them  to  see  their 
prey.  In  storms  these  lantern-fishes  sometimes  lose  their 
bearings  and  are  thrown  upward  to  the  surface. 

In  general  the  more  predatory  in  its  habits  any  fish  is 
the  sharper  its  teeth,  and  the  broader  its  mouth.  Among 
brook-fishes  the  pickerel  has  the  largest  mouth  and  the 
sharpest  teeth.  It  has  been  called  a  "  mere  machine  for 
the  assimilation  of  other  organisms. ' '  The  trout  has  a 
large  mouth  and  sharp  teeth.  It  is  a  swift,  voracious,  and 
predatory  fish,  feeding  even  on  its  own  kind.  The  sunfish 
is  less  greedy  and  its  mouth  and  teeth  are  smaller,  though 
it  too  eats  other  fish. 

As  means  of  escape,  most  fishes  depend  on  their  speed 
in  swimming.  But  some  hide  among  rocks  and  weeds, 
disguising  themselves  by  a  change  in  color  to  match  their 
surroundings.  Others,  like  the  flounders  and  skates,  lie 
flat  on  the  bottom.  Still  others  retreat  to  the  shallows 
or  the  depths  or  the  rock-pools  or  to  any  place  safer  than 
the  open  sea.  Some  are  protected  by  spines  which  they 
erect  when  attacked.  Some  erect  these  spines  only  after 
they  have  been  swallowed,  tearing  the  stomach  of  their 
enemy  and  killing  it,  but  too  late  to  save  themselves. 
Again  in  some  species  the  spines  are  armed  with  poison 
which  benumbs  the  enemy.  Sometimes  an  electric  battery 
about  the  head  or  on  the  sides  gives  the  biting  fish  a 
severe  shock  and  drives  him  away.  Such  batteries  are 
found  in  the  electric  rays  or  torpedo,  in  the  electric  eel 
of  Paraguay,  the  electric  catfish  of  the  Nile,  the  electric 
stargazer  and  other  fishes. 

Some  fishes  are  protected  by  their  poor  and  bitter  flesh. 


BRANCH  CHORD  AT 4;   CLASS  PISCES:    THE  FISHES    287 

Some  have  bony  coats  of  mail  and  sometimes  the  coat  of 
mail  is  covered  with  thorns,  as  in  the  porcupine-fish. 
This  fish  and  various  of  its  relatives  have  the  habit  of  filling 
the  stomach  with  air  when  disturbed,  then  floating  belly 
upward,  the  thorny  back  only  within  reach  of  its  enemies. 
Many  species  (cling  fishes)  attach  themselves  to  the 
rocks  by  a  fleshy  sucking-disk.  Some  (Remora)  (fig.  1 1 8) 
cling  to  larger  fishes  by  a  strange  sucking-disk  on  the  head, 
a  transformed  dorsal  fin,  being  thus  shielded  from  the 


FIG.  118. — The  remora,  or  cling  fish,  Remoropsis  brachyptera.     Note  sucker 
on  top  of  head.     (After  Goode.) 

attacks  of  fish  smaller  than  their  protectors.  Some  small 
fishes  seek  the  shelter  of  the  floating  jellyfishes,  lurking 
among  their  poisoned  tentacles.  Others  creep  into  the 
masses  of  floating  gulf-weed.  Some  creep  into  the  shell 
of  clams  and  snails.  In  the  open  channel  of  a  sponge, 
the  mouth  of  a  tunicate  and  in  similar  cavities  of  various 
animals,  little  fishes  may  be  found.  A  few  fishes  (hag- 
fishes)  are  parasitic  on  others,  boring  their  way  into  the 
body  and  devouring  the  muscles  with  their  rasp-like 
teeth. 

Some  fishes  are  provided  with  peculiar  modifications  of 
the  gills  which  enable  them  to  breathe  for  a  time  out  of 
water.  Such  fish  have  the  pectoral  fins  modified  for  a 
rather  poor  kind  of  locomotion  on  land,  thus  enabling 
them  to  move  from  pond  to  pond  or  from  stream  to  stream. 
In  cold  climates  the  fishes  must  either  migrate  to  warmer 
latitudes  in  winter,  as  some  do,  or  withstand  variously  the 
cold,  often  freezing  weather.  Some  fish  can  be  frozen 


288  ELEMENTARY  ZOOLOGY 

solid,  and  yet  thaw  out  and  resume  active  living.  Some 
lie  at  the  bottoms  of  deep  pools  through  the  colder  periods, 
while  many  others,  such  as  the  minnows,  chubs,  and 
other  kinds  common  in  small  streams,  bury  themselves  in 
the  mud,  and  lie  dormant  or  asleep  through  the  whole 
winter.  On  the  other  hand  in  countries  where  the  long 
intense  rainless  summers  dry  up  the  pools,  some  fishes 
have  the  habit  of  burying  themselves  in  the  mud,  which, 
with  slime  from  the  body,  forms  about  them  a  sort  of  tight 
cement  ball  in  which  they  lie  dormant  until  the  rains 
come.  "  Thus  a  lung-fish  (called  Protopterus),  found  in 
Asia  and  Africa,  so  completely  slimes  a  ball  of  mud 
around  it  that  it  may  live  for  more  than  one  season,  per- 
haps many;  it  has  been  dug  up  and  sent  to  England,  still 
enclosed  in  its  round  mud-case,  and  when  it  was  placed 
in  warm  water  it  awoke  as  well  as  ever." 

Food-fishes  and  fish-hatcheries. — Most  fishes  are  suit- 
able for  food,  though  not  all.  Some  are  too  small  to  be 
worth  catching  or  too  bony  to  be  worth  eating.  Some 
of  the  larger  ones,  especially  the  sharks,  are  tough  and 
rank.  A  few  are  bitter  and  in  the  tropics  a  number  of 
species  feed  on  poisonous  coelenterates  about  the  coral 
reefs,  becoming  themselves  poisonous  in  turn.  But  a  fish  is 
rarely  poisonous  or  unwholesome  unless  it  takes  poisonous 
food.  Where  fishes  of  a  kind  specially  used  for  food  gather 
in  great  numbers  at  certain  seasons  of  the  year,  fishing  is 
carried  on  extensively  and  with  an  elaborate  equipment. 
Such  fisheries,  some  of  which  have  been  long  known,  are 
scattered  all  over  the  world.  Along  the  shores  of  the 
Mediterranean  Sea,  and  on  the  coasts  of  Norway,  France, 
the  British  Isles  and  Japan  are  numerous  great  fishing- 
places.  But  "  nowhere  are  there  found  such  large  fisheries 
as  those  along  the  northern  Atlantic  coasts  of  our  own 
continent,  extending  from  Massachusetts  to  Labrador. 
Especially  on  the  banks  of  Newfoundland  are  codfish, 


BRANCH   CHORD  AT  A;   CLASS   PISCES:    THE  FISHES     289 

herring,  and  mackerel  caught. ' '  Among  our  fresh-water 
fisheries  the  great  salmon  fisheries  of  the  Penobscot  and 
Columbia  rivers  and  of  the  Karluk  and  other  rivers  of 
Alaska  are  the  best  known.  The  whitefish  of  our  Great 
Lakes  is  also  one  of  the  important  food-fishes  of  the  world. 

In  many  places  fishes  are  raised  in  so-called  hatcheries, 
not  usually  for  immediate  consumption  but  for  the  purpose 
of  stocking  ponds  and  streams  either  in  the  neighborhood 
of  the  hatchery  or  in  distant  waters  which  the  special 
species  cultivated  has  not  been  able  naturally  to  reach. 
The  eggs  of  some  fishes  are  large  and  non-adherent,  two 
features  which  greatly  favor  artificial  impregnation  and 
hatching.  In  the  hatcheries  the  eggs  are  put  first  into 
warm  water,  where  development  begins;  they  are  then 
removed  into  cool  water,  which  arrests  development  with 
out  injury,  making  shipment  possible.  The  eggs  of 
salmon  and  trout  in  particular  can  be  sent  long  distances 
to  suitable  streams  or  ponds.  The  eggs  of  the  shad  have 
been  thus  carried  from  the  East  to  the  streams  of  Cali- 
fornia and  trout  have  been  distributed  to  many  streams  in 
our  country  which  by  themselves  they  could  never  have 
reached. 

The  salmon  is  a  conspicuous  example  of  those  fishes 
which  can  be  artificially  propagated.  The  eggs  of  the 
salmon  are  large,  firm,  and  separate  from  each  other.  If 
the  female  fish  be  caught  when  the  eggs  are  ripe  and 
her  body  be  pressed  over  a  pan  of  water  the  eggs  will 
flow  out  into  the  water.  By  a  similar  process  the  milt  or 
male  sperm-cells  can  be  procured  and  poured  over  the 
eggs  to  fertilize  them.  The  young  after  hatching  are  kept 
for  a  few  days  or  weeks  in  artificial  pools,  till  the  yolk- 
sacs  are  absorbed  and  they  can  take  care  of  themselves. 
They  are  then  turned  into  the  stream,  where  they  drift  tail 
foremost  with  the  current  and  pass  downward  to  the  sea. 
All  trout  may  be  treated  in  similar  fashion,  but  there  are 


2 90  .       ELEMENTARY  ZOOLOGY 

many  food-fishes  which  cannot  be  handled  in  this  way. 
In  some  the  eggs  are  small  or  soft,  or  viscid  and  adhering 
in  bunches.  In  others  the  life-habits  make  artificial  fer- 
tilization impossible.  Such  species  are  artificially  reared 
only  by  catching  the  young  and  taking  them  from  one 
stream  to  another.  To  this  type  belong  the  black  bass, 
the  sunfish,  the  catfish  and  other  familiar  forms. 


CHAPTER   XXV 

BRANCH    CHORDATA    (Continued).       CLASS   BA- 
TRACHIA:    THE    BATRACHIANS 

THE  structure,  life-history,  and  habits  of  the  garden- 
toad  (Bnfo  Icntiginosus}  have  already  been  studied  (see 
Chapter  II  and  Chapter  XII). 

OTHER    BATRACHIANS. 

The  class  Batrachia  includes  the  animals  familiarly 
known  as  coecilians,  sirens,  mud-puppies,  salamanders, 
toads,  and  frogs.  Although  differing  plainly  from  fishes 
in  appearance  and  habits,  the  batrachians  are  really  closely 
related  to  them,  resembling  them  in  all  but  a  few  essential 
characters.  Among  the  distinctive  characters  of  ba- 
trachians may  be  noted  the  absence  of  fins  supported 
by  fin-rays,  the  presence  usually  of  well-developed  legs 
for  walking  or  leaping,  and  the  absence  or  reduction  of 
certain  bones  of  the  head  connected  with  the  gills  and 
lower  jaw  and  which  are  well  developed  in  the  fishes. 
The  batrachians  stand  in  somewhat  intermediate  position 
between  the  fishes  and  the  reptiles,  showing  some  of  the 
characters  of  both.  They  are,  like  fishes  and  reptiles, 
cold-blooded.  In  their  adult  condition  some  are  terres- 
trial and  some  aquatic  as  to  habitat,  but  all  have  an  aquatic 
larval  life.  The  water-inhabiting  young  breathe  at  first 
by  means  of  gills,  later  lungs  begin  to  develop,  and  for  a 
time  both  gills  and  lungs  are  used  in  respiration.  Finally 
in  the  adult  condition  in  almost  all  of  the  forms  the  gills 

291 


292  ELEMENTARY  ZOOLOGY 

are  wholly  lost  and  breathing  is  done  by  the  lungs  and 
skin  solely.  Correlated  with  the  change  of  habits  from 
larval  to  adult  stage  there  is  usually  a  well-marked  meta- 
morphosis in  post-embryonic  development.  This  meta- 
morphosis is  specially  striking  among  the  frogs  and  toads. 
None  of  the  aquatic  forms  is  marine,  salt  water  always 
killing  eggs,  larva?  or  adults.  Batrachians  are  found  all 
over  the  world,  although  there  are  few  in  the  extreme 
North.  They  are  most  abundant  in  warm  and  tropical 
lands. 

Body  form  and  organization. — The  body  varies  from 
a  long  and  slender,  truly  snake-like  form  as  in  the  tropical 
ccecilians  through  the  usual  salamander  (fig.  119)  shape, 
where  it  is  more  robust  but  still  elongate  and  tailed,  to 
the  heavy,  squat,  tailless  condition  of  the  toads.  Legs, 


FIG.  119. — The  tiger  salamander.      (From  Jenkins  and  Kellogg.) 

with  five  digits,  are  usually  present,  and  are  used  for 
swimming,  walking,  or  leaping.  The  legs  are  longest 
and  best  developed  in  the  short  tailless  frog  and  toad 
forms  which  are  mostly  terrestrial,  and  are  short  and  weak 
in  the  tailed  salamander  forms,  many  of  which  are  aquatic. 
The  skin  is  almost  always  naked,  showing  a  marked  differ- 
ence from  the  scaled  condition  of  reptiles  and  most  of  the 
fishes,  and  its  cells  secrete  a  slimy,  sticky,  usually  whitish 
fluid,  which  in  some  cases  is  irritating,  or  even  poisonous. 


BRANCH  CHORDATA:   CLASS  BATRACHIA  293 

The  skin  is  sometimes  thrown  up  into  folds  or  ridges,  and 
in  some  species  is  elevated  to  form  a  kind  of  fin  on  the 
tail  or  back.  This  unpaired  fin  differs  from  the  dorsal  fin 
(and  other  fins)  of  fishes  in  not  being  supported  by  rayed 
processes  of  the  skeleton.  There  are  in  some  batrachians 
traces  of  an  exoskeleton  in  the  presence  of  scale-like 
structures  in  the  skin  or  in  the  horny  nails  on  the  digits, 
but  these  cases  are  rare.  The  skin  contains  pigment-cells 
and  many  of  the  batrachians  are  brilliantly  colored  and 
patterned ;  some  of  the  pigment  is  carried  by  special  con- 
tractile or  expansile  cells,  the  chromatophores  (see 
account  of  chromatophores  of  the  Cephalopoda,  p.  256), 
so  that  the  animal  can  change  its  tint  and  markings  more 
or  less  rapidly.  All  the  batrachians  possess  external  gills 
in  their  aquatic  larval  stage,  and  in  a  few  forms,  as  the 
sirens  and  mud-puppies,  gills  are  retained  all  through  life. 
These  gills  are  branched  folds  of  the  skin  abundantly 
supplied  with  blood-vessels. 

In  the  organization  of  the  batrachian  body  the  usual 
vertebrate  characters  appear,  the  body-organs  being 
arranged  with  reference  to  a  supporting  and  protecting 
internal  bony  skeleton.  The  head  is  plainly  set  off  from 
the  rest  of  the  body  and  bears  the  mouth  and  the  organs 
of  hearing  and  sight.  Certain  so-called  lateral  sense 
organs,  the  function  of  which  is  not  exactly  known,  occur 
arranged  in  three  lines  on  each  side  of  the  body  of  some 
of  the  forms.  Both  pairs  of  limbs  are  present  and  func- 
tional in  almost  all  of  the  species.  In  the  coecilians  the 
limbs  are  wholly  wanting ;  in  the  sirens  only  the  fore  legs 
are  present. 

Structure. — The  most  obvious  skeletal  differences 
among  batrachians  are  those  due  to  variations  in  external 
form.  While  there  are  as  many  as  100  vertebra,*  in  some 
of  the  elongate  long-tailed  salamanders  (even  250  in  the 
strange  snake-like  ccecilians),  there  are  but  10  (the  last 


294  ELEMENTARY  ZOOLOGY 

or  tenth  being  the  rod-shaped  bone  called  the  urostyle) 
in  the  short,  tailless  frogs  and  toads.  To  any  of  the 
vertebrae  except  the  first  (the  single  cervical  vertebra)  and 
the  last,  ribs  may  be  attached  and  the  ccecilians  have 
about  as  many  pairs  of  ribs  as  vertebrae.  In  the  frogs 
and  toads,  however,  the  ribs  are  lost.  In  any  case  they 
are  never  fastened  by  their  lower  ends  to  the  breast-bone. 

The  alimentary  canal  is  usually  not  much  longer  than 
the  body  and  is  plainly  divided  into  mouth,  pharynx, 
oesophagus,  small  intestine,  large  intestine  or  rectum, 
and  anal  opening.  The  teeth  when  present  occur  on  both 
the  jaws  and  the  palate.  They  are  small,  sharp,  point 
backward  and  are  fused  to  the  bones.  They  are  wholly 
wanting  in  the  toad  and  in  some  other  allied  forms.  The 
tongue  may  be  wanting,  or  may  be  immovably  fixed  to 
the  floor  of  the  mouth,  or  as  in  the  frogs,  fastened  at  its 
front  end  but  free  behind,  so  that  the  hinder  end  can  be 
protruded  far  from  the  mouth  for  the  purpose  of  catching 
insects. 

The  organs  of  respiration  are  gills,  external  and  in- 
ternal, lungs,  trachea  or  windpipe,  and  the  skin.  In  the 
earliest  larval  stages  all  batrachians  have  gills;  later,  in 
most  cases,  the  gills  become  reduced  and  disappear,  while 
at  the  same  time  lungs  are  developing.  In  some  sala- 
manders the  lungs  never  develop,  but  the  animals,  in  their 
adult  stage,  breathe  wholly  by  means  of  the  skin.  In  a 
few  cases,  as  in  the  siren  and  mud-puppies,  gills  are 
retained  through  the  whole  life,  although  lungs  are  also 
present  in  the  adult  stage.  The  lungs  are  two  in  number, 
a  right  and  a  left  lung,  and  are  simple  sacs  with  the  walls 
more  or  less  folded  or  thrown  into  ridges  and  richly  sup- 
plied with  blood-vessels.  The  front  end  of  the  lungs 
opens  directly  into  the  pharynx  or,  in  the  more  elongate 
batrachians,  is  connected  with  it  by  a  tubular  trachea  or 
windpipe.  In  the  frogs  and  toads  there  are  vocal  cords 


BRANCH  CHORD  AT  A:   CLASS  BATRACHIA  295 

stretched    across    the   short  windpipe;     the    vibration  of 
these  cords  produces  the  croaking. 

The  heart  is  always  three-chambered,  consisting  of  the 
right  and  left  auricles  and  a  single  ventricle.  The  circu- 
lation of  the  more  generalized  salamanders  like  the  mud- 
puppies  is  essentially  like  that  of  a  fish.  In  the  frogs  and 
toads  there  is  a  distinct  advance  beyond  this  condition. 
The  red  corpuscles  of  the  blood  are  oval  in  shape  and  are 
the  largest  found  among  any  of  the  vertebrates. 

In  the  nervous  system  the  small  size  of  the  hindbrain 
or  cerebellum  is  noticeable.  The  sense  organs  are  fairly 
well  developed.  The  skin  of  the  whole  body  is  provided 
with  tactile  nerve-endings.  There  are  special  taste  organs 
on  the  lining  membrane  of  the  tongue  and  mouth-cavity. 
The  eyes  have  no  lids  in  some  of  the  lower  forms ;  most 
of  the  frogs  and  toads  have  an  upper  lid  but  no  under  one, 
although  a  thin  membrane,  called  the  nictitating  mem- 
brane, arises  from  the  lower  margin  of  the  eye  and  can  be 
drawn  up  over  it.  The  ears  have  no  external  parts,  other 
than  the  thin  tympanic  membranes.  The  nostrils  of  frogs 
and  toads  can  be  closed  by  the  contraction  of  certain 
special  muscles. 

Life-history  and  habits. — The  sexes  are  distinct,  and  in 
most  cases  the  young  hatch  from  eggs.  A  few  of  the  sala- 
manders give  birth  to  free  young.  The  eggs  are  usually  in 
strings  or  chains  enclosed  in  a  clear  gelatinous  substance; 
these  chains  of  eggs  are  either  simply  dropped  into  the 
water  or  are  fastened  to  water-plants.  The  young,  called 
tadpoles  (fig.  120),  in  their  earlier  larval  stages  are  ex- 
tremely fish-like  in  character,  long-bodied,  tailed,  swim- 
ming freely  about  by  means  of  the  fin-like  flattened  tail,  and 
breathing  by  means  of  external  gills.  Nor  do  they  show 
any  sign  of  legs.  As  the  tadpoles  grow  and  develop  the 
legs  begin  to  appear,  the  hind  legs  first  in  the  frogs  and 
toads,  the  fore  legs  first  in  the  salamanders ;  lungs  develop 


296  .     ELEMENTARY  ZOOLOGY 

and  the  gills  disappear  (except  in  the  cases  of  the  few  forms 
which  retain  gills  through  life).  The  tail  shortens  and 
finally  disappears  in  the  frogs  and  toads ;  with  the  salaman- 
ders the  tail-fin  only  is  lost.  At  the  same  time  the  change 
from  water  to  land  is  made.  Further  growth  is  very 


FIG.    120. — Tadpoles.       (Photograph   from   life   by  Cherry  Kearton;    per- 
mission of  Cassel  &  Co.) 

slow;  frogs  are  not  really  adult,  that  is,  capable  of  pro- 
ducing young,  until  they  are  five  years  old,  and  they  may 
continue  to  increase  in  size  until  they  are  ten  years  old. 

The  food  of  the  adult  batrachians  is  almost  exclusively 
small  animals,  particularly  insects  and  worms.  Crus- 
taceans, snails,  and  young  fish  are  also  eaten.  The  tad- 
poles also  eat  vegetable  matter.  Almost  all  batrachians 
are  nocturnal  in  habit,  remaining  concealed  by  day.  In 
the  zones  in  which  cold  winters  occur  they  hibernate  or 
pass  the  winter  in  a  torpid  condition,  or  state  of  "  sus- 
pended animation,"  or,  as  it  is  said,  they  sleep  through 
the  winter.  Frogs  burrow  into  the  mud  at  the  bottom  of 
ponds  at  the  approach  of  winter  and  come  forth  early  in 


BRANCH   CHORD  AT  A:   CLASS  B  AT R  A  CHI  A  297 

the  spring-  to  lay  their  eggs.  Most  batrachians  are  very 
tenacious  of  life,  being  able  to  withstand  long  periods  of 
fasting  and  serious  mutilation,  and  most  of  them  can 

t> 

regenerate  certain  lost  parts,  such  as  the  tail  or  legs. 

Classification,— The  living  Batrachia  are  divided  into 
three  orders,  viz.,  the  Urodela,  including  the  sirens,  mud- 
puppies,  salamanders,  and  newts,  batrachians  which  retain 
the  tail  throughout  life,  having  generally  two  pairs  of  limbs 
of  approximately  equal  size,  and  sometimes  possessing 
gills  or  gill-slits  in  the  adult  condition ;  the  Anura,  or 
frogs  and  toads,  with  no  tail  in  the  adult  condition,  with 
short  and  broad  trunk,  with  hind  limbs  greatly  exceeding 
the  fore  limbs  in  size,  and  never  with  gills  or  gill-slits 
in  the  adult  stage;  and  the  Gymnphiona,  or  ccecilians, 
snake-like  batrachians  having  neither  limbs  nor  tail,  with 
a  dermal  exoskeleton  and  without  gills  or  gill-slits  in  the 
adult. 

Mud-puppies,  salamanders,  etc.  (Urodela). —  TECHNI- 
CAL NOTE. — If  possible  obtain  specimens  of  mud-eels  (Siren],  com- 
mon in  the  South,  or  mud-puppies  (Necturus],  common  in  the  cen- 
tral North,  as  examples  of  batrachians  with  gills  persisting  in  the 
adult  stage.  One  or  more  species  of  Amblystoma  may  be  found  in 
almost  any  part  of  the  country,  and  larvae  of  large  size  may  be  found 
with  the  external  gills.  For  an  example  of  the  general  long-tailed 
or  Urodelous  type  of  batrachian  any  salamander  or  newt  occurring 
in  the  vicinity  of  the  school  may  be  used.  The  little  green  triton  or 
eft  (Diemyctylus  viridiscens}  of  the  eastern  States,  or  its  larger 
brown-backed  congener  of  the  Pacific  coast  (D.  torosus]  is  common 
in  water,  while  another  eft,  the  little  red-backed  salamander, 
(Plethodon}  is  common  in  the  woods  under  logs  and  stones.  The 
external  characters  of  the  body  should  be  compared  with  those  of 
the  toad.  The  skeleton  should  be  prepared  by  macerating  away 
the  flesh  (for  directions,  see  p.  452),  and  the  presence  of  the  many 
caudal  vertebrae  and  the  ribs,  the  equality  in  size  of  the  legs,  and 
other  points  should  be  noted.  Compare  with  skeleton  of  toad. 
Make  drawings.  It  will  be  well,  also,  to  dissect  out  and  examine 
the  various  internal  organs  of  the  salamander,  comparing  them  with 
the  same  organs  in  the  toad.  The  salamander,,  indeed,  is  in  many 
ways  better  than  the  toad  as  an  example  of  the  class.  Its  body  is 
less  adaptively  modified  and  shows  the  essentially  fish-like  charac- 
ter of  the  batrachian  structure. 


298  ELEMENTARY  ZOOLOGY 

The  batrachians  which  retain  external  gills  in  the  adult 
stage  are  the  members  of  two  families  of  which  the 
American  representatives  are  known  as  mud-eels  (Siren} 
and  mud-puppies  or  water-dogs  (Necturus)*  The  mud- 
eels,  which  are  found  *  *  in  the  ditches  in  the  swamps  of 
the  southern  States  from  South  Carolina  to  the  Rio  Grande 
of  Texas  and  up  the  Mississippi  as  high  as  Alton,  Illinois, ' ' 
are  blackish  in  color,  have  no  hind  legs  and  are  long  and 
slender,  with  the  tail  shorter  than  the  rest  of  the  body. 
They  reach  a  length  of  nearly  three  feet.  The  mud- 
puppies,  found  in  the  Great  Lakes  and  in  the  rivers  of  the 
upper  Mississippi  valley,  are  brown  with  colored  spots, 
and  are  about  two  feet  long  when  full  grown.  They  have 
both  fore  and  hind  legs. 

A  few  salamanders,  while  not  possessing  external  gills 
when  adult,  have  a  spiracle  or  small  circular  opening  in 
the  side  of  the  neck  which  leads  into  the  throat.  The 
best-known  American  salamander  of  this  kind  is  the 
large  heavy-bodied  blackish  water-dog  or  ' '  hellbender  ' ' 
(Cryptobranchus)  of  the  Ohio  River.  It  is  about  two  feet 
long,  and  is  <4a  very  unprepossessing  but  harmless 
creature."  It  has  a  conspicuous  longitudinal  fold  of  skin 
along  each  side  of  the  body.  The  largest  known  ba- 
trachian,  the  giant  salamander  of  Japan  (Megalobatrachus\ 
reaching  a  length  of  three  feet,  is  related  to  the  water- 
dog. 

Of  all  the  salamanders  the  most  interesting  are  the 
blunt-nosed  salamanders  (Amblystoma}.  A  dozen  or 
more  species  of  A mblystoma  occur  in  North  America,  of 
which  tigrimim,  a  dark-brown  species  with  many  irregular 
yellow  blotches  sometimes  arranged  in  cross-bands,  is  the 
most  widespread.  The  larvae  of  some  Amblystoma  retain 
their  gills  until  they  have  reached  a  large  size,  and  in  one 
or  two  species  the  usual  metamorphosis  is  very  long 
delayed  and  the  salamanders  produce  young  while  in  the 


BRANCH   CHORD  AT  A  :   CLASS  BATRACHIA  299 

larval  condition,  that  is,  while  retaining  the  gills  and  a 
compressed  fin-like  tail.  In  the  case  of  a  certain  Mexican 
species  (A.  maculatunt)  it  is  believed  that  the  final  meta- 
morphosis never  occurs.  The  Mexicans  call  these  gilled 
larval  Amblystoma  axolotls,  and  use  them  for  food.  For 


FIG.   121. — The  Western  brown  eft,   or  salamander,  Diemyctyhis  torosus. 
(From  living  specimen.) 

a  long  time  naturalists  supposed  the  Amblystoma  larvae 
which  produce  young  to  be  the  adults  of  a  species  of  sala- 
manders which  retained  their  gills  through  life,  like  the 
sirens  and  mud-puppies,  and  classified  them  in  a  distinct 
genus. 

Of  the  various  common  salamanders  or  newts  some  are 
found  in  streams,  ponds,  and  ditches,  and  some  under 
logs  and  stones  in  the  woods.  The  aquatic  forms  have 
the  tail  compressed  (flattened  from  side  to  side),  while 
the  land  forms  have  the  tail  cylindrical,  tapering  to  a 
point.  Most  of  the  land-salamanders  produce  their  young 
alive,  while  the  water  forms  lay  eggs  which  are  usually 
attached  to  a  submerged  plant-stem.  The  salamanders 
are,  almost  without  exception,  found  only  in  the  northern 
hemisphere. 

Frogs  and  toads  (Anura).— There  are  about  a  dozen 
species  of  frogs  in  the  United  States.  The  largest  of 
these,  and  indeed  the  largest  of  all  the  frogs,  is  the  well- 
known  bullfrog  (Rana  catesbiand],  which  reaches  a  length 
(head  to  posterior  end  of  body)  of  eight  inches.  It  is 
found  in  ponds  and  sluggish  streams  all  over  eastern 


300  ELEMENTARY  ZOOLOGY 

United  States  and  in  the  Mississippi  valley.  It  is  green- 
ish in  color  with  the  head  usually  bright  pale  green.  Its 
croaking  is  very  deep  and  sonorous.  The  pickerel-frog 
(R.  palustris],  which  is  bright  brown  on  the  back  with  two 
rows  of  large  oblong  square  blotches  of  dark  brown  on 
the  back,  is  found  in  the  mountains  of  eastern  United 
States.  The  little  pale  reddish-brown  wood-frog  (R.  syl- 
vaticd)  with  arms  and  legs  barred  above  is  common  in 
damp  woods  and  is  "an  almost  silent  frog."  The 
peculiar  and  infrequently  seen  frogs  known  as  the  '  *  spade- 
foots  ' '  (Scaphiopus}  are  subterranean  in  habit  and  usually 
live  in  dry  fields  or  even  on  arid  plains  and  deserts. 
They  pass  through  their  development  and  metamorphosis 
very  rapidly,  appearing  immediately  after  a  rain  and  lay- 
ing their  eggs  in  temporary  pools.  At  this  time  of  egg- 
laying  they  utter  extraordinarily  loud  and  strange  cries. 
Some  frogs  in  other  parts  of  the  world  live  in  trees,  and 
the  eggs  of  one  species  are  deposited  on  the  leaves  of 
trees,  leaves  which  overhang  the  water  being  selected  so 
that  the  issuing  young  may  drop  into  it. 

The  true  tree-frogs  or  tree-toads  (Hylidae)  constitute  a 
family  especially  well  represented  in  tropical  America. 
They  have  little  disk-  or  pad-like  swellings  on  the  tips  of 
their  toes  to  enable  them  to  hold  firmly  to  the  branches 
of  the  trees  in  which  they  live.  Some,  like  the  swamp 
tree-frog  and  the  cricket-frog,  are  not  arboreal  in  habit, 
remaining  almost  always  on  the  ground.  The  common 
tree-frog  of  the  eastern  States  (Hyla  vcrsicolor)  is  green, 
gray,  or  brown  above  with  irregular  dark  blotches,  and 
yellow  below.  It  croaks  or  trills,  especially  at  evening 
and  in  damp  weather.  Pickering's  tree-frog  (Hyla 
pickeringii}  makes  the  "first  note  of  spring"  in  the 
eastern  States.  This  tree-frog  is  the  one  most  frequently 
heard  in  the  autumn  too,  but  "its  voice  is  less  vivacious 
than  in  the  spring  and  its  lonely  pipe  in  dry  woodlands  is 


BRANCH  CHORD AT A:   CLASS  BATRACHIA  301 

always  associated  with  goldenrods  and  asters  and  falling 
leaves. ' '  The  tree-frogs  of  North  America  lay  their  eggs 
in  the  water  on  some  fixed  object  as  an  aquatic  plant,  in 
smaller  packets  than  those  of  the  true  frogs,  and  not  in 
strings  as  do  the  toads. 

The  toads  (Bufonidae)  differ  from  the  true  frogs  in 
having  no  teeth  and  in  not  having,  as  the  frogs  do,  a 
cartilaginous  process  uniting  the  shoulder-bones  of  the 
two  sides  of  the  body.  The  absence  of  this  uniting 
process  makes  the  thoracic  region  capable  of  great  expan- 
sion. There  are  only  a  few  species  of  toads  in  North 
America,  but  one  of  these  species,  the  common  American 
toad  (Bufo  lentiginosus),  is  very  abundant  and  wide- 
spread. It  appears  also  in  two  or  three  varieties,  the 
common  toad  of  the  southern  States  differing  in  several 
particulars  from  that  of  the  northern.  The  toad  is  a 
familiar  inhabitant  of  gardens,  and  does  much  good  by 
feeding  on  noxious  insects.  It  is  most  active  at  twilight. 
Its  eggs  are  laid  in  a  single  line  in  the  centre  of  a  long 
slender  gelatinous  string  or  rope,  which  is  nearly  always 
tangled  and  wound  round  some  water-plant  or  stick  near 
the  shore  on  the  bottom  of  a  pond.  The  eggs  are  jet 
black  and  when  freshly  laid  are  nearly  spherical.  At  the 
time  of  egg-laying  the  toads  croak  or  call,  making  a  sort 
of  whistling  sound  and  at  the  same  time  pronouncing  deep 
in  the  throat  "  bu-rr-r-r-r. "  The  toad  does  not  open  its 
mouth  when  croaking,  but  expands  a  large  sac  or  resonator 
in  its  throat.  The  toad-tadpoles  are  blacker  than  those 
of  frogs  or  salamanders,  and  undergo  their  metamorphosis 
while  of  smaller  size  than  those  of  frogs.  When  they 
leave  the  water  they  travel  for  long  distances,  hopping 
along  so  vigorously  that  in  a  few  days  they  may  be  as  far 
as  a  mile  from  the  pond  where  they  were  hatched.  They 
conceal  themselves  by  day,  but  will  appear  after  a  warm 
shower;  this  sudden  appearance  of  many  small  toads 


3° 2  ELEMENTARY  ZOOLOGY 

sometimes  gives   rise   to  the  false   notion   that  they  have 
fallen  with  the  rain. 

Coecilians  (Gymnophiona). — The  third  order  of  ba- 
trachians,  the  ccecilians,  includes  about  twenty  species  of 
slender  worm-  or  snake-like  limbless  forms  which  are 
confined  to  the  tropics.  Some  of  them  are  wholly  blind 
and  the  others  have  only  rudimentary  eyes.  In  them  the 
skin  is  folded  at  regular  intervals  so  that  the  body  appears 
to  be  rigid  or  segmented,  and  in  some  species  there  are 
small  concealed  horny  scales  in  the  skin. 


CHAPTER    XXVI 

BRANCH  CHORDATA  (Continued}.  CLASS  REP- 
TILIA:  THE  SNAKES,  LIZARDS,  TURTLES, 
CROCODILES,  ETC. 

THE   GARTER  SNAKE   (Thamnophis   sp.) 

TECHNICAL  NOTE. — Garter  snakes  may  be  found  almost  any- 
where during  the  spring  and  summer  months.  If  possible  each 
student  should  have  a  specimen,  but  in  case  it  is  difficult  to  get 
enough  snakes  two  students  can  use  a  single  specimen.  If  garter 
snakes  are  rare,  take  any  other  snake.  Snakes  will  live  a  long  time 
without  feeding  and  specimens  should  be  kept  alive  until  ready  to 
use.  Kill  with  chloroform  as  directed  for  the  toad  (p.  5).  After 
completing  the  study  of  the  external  characters  place  each  specimen 
in  a  dissecting-pan  and  with  a  pair  of  scissors  cut  through  the  scales 
on  the  ventral  side,  passing  backwards  from  the  eighteenth  to  the 
fortieth.  Pin  back  the  edges  of  the  cut  and  thus  expose  the  heart. 
Through  its  lower  end,  the  ventricle,  insert  a  large  canula;  inject 
with  a  fairly  large  syringe  the  glue  mass  which  is  described  on 
p.  452.  This  injection  will  fill  the  entire  arterial  system.  To  inject 
the  venous  system  make  another  cut  through  the  ventral  scales,  cut- 
ting forward  from  the  anal  scale  through  about  forty  of  them.  Note 
the  injected  mass  in  some  of  the  vessels  already  filled.  Take  one 
of  the  large  vessels  still  containing  blood  and  pass  two  ligatures 
beneath  it.  Get  ready  a  small  canula  and  cut  a  slit  in  the  vessel, 
elevating  the  head  so  that  the  blood  will  run  out  as  much  as  possi- 
ble. Now  wash  the  blood  off,  insert  the  canula  in  the  slit  and  tie 
one  ligature  about  the  vessel  containing  the  canula  ;  have  the  other 
ready  to  tie  after  the  vein  has  been  injected.  Use  a  new  color  for 
the  venous  system.  Leave  specimen  in  cold  water  for  a  time  until 
the  injection  is  hard.  Then  continue  the  cut  from  the  anal  plate 
forward  to  the  lower  jaw  and  pin  out  the  edges  of  the  cut  on  both 
sides  in  the  dissecting-pan. 

Structure  (fig.  122). — Note  that  the  snake  is  covered 
with  horny  scales  somewhat  as  the  fish  is.  How  do  these 
scales  differ  from  those  of  the  fish  ?  In  snakes  the  scales 

303 


3^4  ELEMENTARY  ZOOLOGY 

are  not  bony,  but  are  true  skin  structures.  Note  the  modi- 
fication of  the  scales  on  the  head,  back,  and  ventral  sur- 
face. Those  on  the  dorsal  surface  often  have  minute 
ridges,  the  keels.  How  do  the  ventral  scales  differ  from  the 
dorsal  ones  and  others  ?  By  a  system  of  muscles  these 
ventral  scales  are  rhythmically  moved  and  as  their  posterior 
edges  are  pushed  back  against  some  resisting  object  the 
body  glides  forward.  On  the  head  note  the  pair  of  eyes. 
Are  there  eyelids  ?  In  front  of  each  eye  note  an  opening. 
What  are  these  openings  ?  Thrust  a  bristle  into  the 
opening  and  see  where  it  enters  the  mouth-cavity  through 
the  internal  nares.  Does  the  snake  have  external  ears  ? 
Observe  the  very  long  jaws  and  note  that  they  are  loosely 
hinged.  Examine  the  inside  of  the  mouth.  Are  there 
teeth?  If  so  where  are  they  situated,  and  how  arranged? 
Note  that  all  of  the  teeth  point  backwards.  Food  is  not 
chewed.  When  some  object  of  prey,  a  frog,  or  mouse, 
for  example,  is  seized,  the  teeth  hold  it  fast  to  the  roof  of 
the  mouth  and  by  a  backward  and  forward  movement  of 
the  lower  jaws  it  is  gradually  drawn  into  the  large 
oesophagus.  What  is  the  character  and  situation  of  the 
tongue  f  Just  behind  the  tongue  note  the  narrow  slit, 
glottis,  opening  into  the  tvindpipc,  or  trachea.  Back  o/ 
the  trachea  opens  the  oesophagus. 

When  the  snake  is  laid  open  the  elongate  heart  will 
be  conspicuous  in  the  anterior  third  of  the  body.  Insert 
a  blowpipe  or  quill  into  the  glottis  just  back  of  the  tongue, 
and  inflate  the  lung,  which  is  a  long,  thin- walled  bag 
extending  from  the  region  of  the  heart  posteriorly  for 
two-thirds  of  the  length  of  the  body.  There  is  but  one 
developed  lung,  the  right ;  note  at  the  anterior  end  of  the 
lung  a  small  mass  of  tissue,  the  atrophied  left  lung. 
Running  forward  from  the  lung  is  a  long  tube  composed 
of  incomplete  cartilaginous  rings,  connected  by  mem- 
brane, the  trachea.  Note  the  long  straight  alimentary 


BRANCH  CHORDATA:   CLASS  REPTILIA  305 

tonal.      Distinguish    the    oesophagus,    stomach,    intestine, 
rectum  and  the  anus. 

In  the  region  of  the  lung  is  an  elongated  dark-red 
glandular  mass,  the  liver.  The  secretion  from  the  liver 
passes  down  through  the  long  Jiepatic  duct  to  the  oval- 
shaped  green  gall-bladder  and  into  the  intestine. 

TECHNICAL  NOTE. — The  bile-duct  may  he  injected  through  the 
jail-bladder  with  some  colored  injecting  mass. 

Note  that  the  duct  running  off  from  the  gall-bladder  to 
the  intestine  passes  through  a  pink  glandular  organ,  the 
Pancreas.  At  the  anterior  end  of  the  pancreas  is  a  dark- 
red  nodular  structure,  the  spleen.  The  alimentary  canal, 
the  liver  and  the  spleen  are  all  suspended  from  the  dorsal 
wall  of  the  body-cavity  by  a  delicate  sheet  of  tissue. 
What  is  this  ?  This  condition  we  have  also  noted  in  the 
toad  and  fish. 

Toward  the  posterior  end  of  the  bod^cavity.  are  two 
long,  dark-red  glands,  the  kidneys,  which  are  the  j*in- 
:ip:il  excretory  organs  of  the  body.  Through  a  long, 
slender  tube  (the  ureter}  each  of  the  kidneys  passes  off  its 
wastes.  Where  do  the  ureters  open  ? 

Anterior  to  the  kidneys  are  the  reproductive  organs. 
The  eggs,  produced  by  the  female  snake,  after  being 
fertilized,  pass  backward  through  the  egg-tubes.  During 
the  breeding  season  these  tubes  are  much  distended. 
This  is  due  to  the  presence  of  the  developing  eggs,  for 
the  young  snakes  are  hatched  in  the  egg-tubes. 

A  successful  injection  as  directed  in  the  first  technical 
note  will  have  filled  both  arterial  and  venous  systems. 
How  does  the  general  shape  of  the  snake's  heart  compare 
with  that  of  the  toad  ?  The  heart  consists  of  two  ven- 
tricles, incompletely  separated,  and  two  auricles.  In  the 
snake  the  conus  arteriosus  is  very  much  shortened  and  is 
not  visible.  Note  two  large  vessels  arising  from  the 


306  ELEMENTARY  ZOOLOGY 

median  portion  of  the  ventricle.  The  one  on  the  left  side 
is  the  left  aortic  artery  or  left  aortic  arch,  while  the  right 
gives  off  two  branches.  Where  does  the  anterior  one  of 
these  run  ?  The  main  branch,  or  right  aortic  arcJi,  passes 
back  to  meet  its  fellow,  the  left  aortic  artery,  forming  with 
it  the  dorsal  aorta,  which  runs  posteriorly  to  the  end  of  the 
tail.  Note  the  various  branches  given  off  by  the  dorsal 
aorta  and  trace  some  of  them.  Arising  from  the  ventricles 
beneath  the  two  aortic  arches  is  the  pulmonary  artery, 
which  goes  to  the  lung.  There  the  blood  is  purified,  after 
which  it  is  taken  up  by  the  pulmonary  vein  and  carried 
back  to  the  left  auricle,  whence  it  passes  into  the  ventricle 
to  be  mixed  with  the  impure  blood  from  the  right  auricle. 
From  the  arteries  the  blood  flows  to  all  parts  of  the  body 
through  fine  capillaries,  bathing  the  tissues,  giving  off 
oxygen  and  taking  up  the  carbonic  acid  gas.  From  these 
capillaries  it  passes  into  veins  and  so  back  to  the  heart; 
from  the  anterior  end  of  the  body  through  the  jugular 
veifo  and  from  the  posterior  portion  of  the  body  through 
the  postcaval  vein.  Flowing  forward  from  the  tail  in  the 
caudal  vein,  the  blood  enters  the  capillaries  of  the  kidneys, 
where  the  waste  matter  is  taken  from  it.  This  part  of  the 
circulatory  system  is  known  as  then?;m/-/<?rta/circulation. 
From  the  kidneys  the  blood  flows  through  the  postcaval 
vein  anteriorly  to  the  heart. 

The  blood  which  passes  out  from  the  dorsal  aorta  to  all 
parts  of  the  alimentary  canal  is  again  collected  into  veins 
which  unite  to  form  the  mesenteric  vein.  This  vein  runs 
to  the  liver,  where  it  breaks  up  into  capillaries.  Thence 
the  blood  is  carried  into  the  postcaval  vein,  which  leads 
directly  to  the  heart.  This  part  of  the  circulatory  system 
which  collects  blood  from  the  alimentary  canal  and  carries 
it  to  the  liver  is  called  the  hepatic-portal  system. 

Just  in  front  of  the  heart  will  be  noted  a  nodular  struc- 
ture, the  thyroid  gland,  while  a  little  in  advance  of  the 


BRANCH  CHORDATA:   CLASS  REPTILIA  3°7 

thyroid  may  be  seen  a  long  glandular  mass,  the  tJiymus 
gland.  The  functions  of  these  glands  are  not  certainly 
understood. 

Remove  the  alimentary  canal  and  muscles  from  a  part 
of  the  body  and  note  that  the  axial  skeleton,  like  that  of 
the  other  vertebrates  studied,  consists  of  a  series  of  verte- 
bra placed  end  to  end.  Are  there  arms  or  legs  ?  Are 
shoulder  and  pelvic  girdles  present  ?  How  many  of  the 
vertebrae  bear  ribs  ?  The  ribs  connect  at  their  lower  ends 
with  the  ventral  scales.  Note  the  great  number  of  the 
vertebrae  and  ribs  as  compared  with  those  of  the  toad  or 
fish.  What  are  those  vertebrae  called  which  bear  no  ap- 
pendages or  ribs  ?  Examine  carefully  the  elongated  skull 
of  the  snake,  especially  the  modified  jaws.  A  detailed 
study  of  the  skeleton  may  be  made  by  referring  to 
the  account  of  the  skeleton  of  the  lizard  in  Parker's 
"  Zootomy,  "  pp.  130  ct  seq. 

The  nervous  system  may  be  worked  out  in  a  specimen 
which  has  been  immersed  in  20  per  cent  nitric  acid.  The 
description  of  the  nervous  system  of  the  toad  (see  pp.  1 2- 
13)  will  suffice  for  a  guide  to  the  study  of  the  nervous 
system  of  the  snake.  The  special  sense  organs,  as  eyes 
and  ears,  should  be  examined  and  compared  with  those 
of  the  fish  and  toad. 

Life-history  and  habits.— The  garter  snakes  are  more 
or  less  aquatic  in  habit  and  are  good  swimmers.  They 
are  often  found  far  from  water,  but  in  greatest  abundance 
where  the  cat-tails  and  rushes  grow  thickest.  They  feed 
on  frogs,  salamanders,  and  field-mice,  which  they  swallow 
whole.  All  the  garter  snakes  are  ovoviviparous,  i.e., 
hatch  eggs  within  the  body-cavity.  The  eggs,  often  as 
many  as  eighteen  or  twenty,  are  enclosed  within  widened 
portions  of  the  oviducts  during  embryonic  existence;  when 
the  young  are  born  they  are  able  to  shift  for  themselves. 
During  cold  weather  the  garter  snake  hibernates,  hiding 


o8  ELEMENTARY  ZOOLOGY 


then  in  some  gopher-hole,  or,  in  the  warmer  climates, 
under  some  log  or  stone,  there  to  lie  dormant  until  the 
warm  days  of  spring  come,  when  it  resumes  activity. 

The  garter  snake  sheds  its  skin  at  least  once  a  year, 
sometimes  oftener.  This  process  may  be  observed  in 
snakes  kept  in  confinement.  For  some  time  before  molt- 
ing the  animal  remains  torpid,  the  eyes  become  milky, 
and  the  skin  loses  its  lustre.  After  a  few  days  it  conceals 
itself,  the  skin  about  the  lips  and  snout  pulls  away  and  the 
animal  slips  out  of  its  entire  skin.  The  snake  not  only 
sheds  the  skin  of  the  body  but  also  the  covering  of  the 
eyes.  Snakes  have  no  eyelids,  as  we  have  already  noted, 
that  which  represents  the  eyelid  being  a  transparent 
membrane  which  covers  the  eyeball. 

No  species  of  the  garter  snake  group  is  poisonous. 
Sometimes  a  garter  snake  may  appear  to  be  vicious,  but 
its  teeth  are  very  short  and  at  best  it  can  only  make  a 
small  scratch  scarcely  piercing  the  skin. 

OTHER    REPTILES. 

The  class  Reptilia  includes  the  lizards,  snakes,  tortoises, 
turtles,  crocodiles,  and  alligators.  Although  popularly 
associated  in  the  common  mind  with  the  batrachians,  the 
reptiles  are  really  more  nearly  related  to  the  birds  than 
to  the  salamanders  and  frogs.  In  general  shape  they 
more  nearly  resemble  the  batrachians,  but  in  the  structural 
condition  of  the  internal  body  organs  they  are  more  like 
the  birds.  They  are  cold-blooded,  and  breathe  exclu- 
sively by  means  of  lungs,  the  forms  which  live  in  water 
coming  to  the  surface  to  breathe.  They  are  covered  with 
horny  scales  or  plates,  which  with  the  entire  absence  of 
gills  after  hatching  readily  distinguish  them  from  all  the 
batrachians.  While  most  reptiles  live  on  land,  some  in- 
habit fresh  water  and  some  the  ocean.  As  the  young 


BRANCH  CHORDATA:   CLASS  REPTILIA  309 

have  the  same  habitat  and  general  habits  as  the  adult, 
there  is  no  such  metamorphosis  in  their  life-history  as  is 
shown  by  the  batrachians.  The  reptiles  are  widespread 
geographically,  occurring,  however,  in  greatest  abund- 
ance in  tropical  regions,  and  being  wholly  absent  from  the 
Arctic  zone.  They  are  not  capable  of  such  migrations 
as  are  accomplished  by  the  birds  and  many  mammals, 
but  withstand  severely  hot  or  cold  seasons  by  passing  into 
a  state  of  suspended  animation  or  seasonal  sleep  or  torpor. 


FIG.  123. — A  lizard  in  the  grass.     (Photograph  from  life  by  Cherry  Kear- 
ton;  permission  of  Cassell  &  Co.) 

Body  form  and  organization. — The  chief  variations  in 
body  form  among  the  reptiles  are  manifest  when  a  turtle, 
lizard,  and  snake  are  compared.  In  the  turtles,  the  body 
is  short,  flattened,  and  heavy,  and  provided  always  with 
four  limbs,  each  terminating  in  a  five-toed  foot;  in  the 
lizards  the  body  is  more  elongate  and  with  usually  four 
legs,  but  sometimes  with  two  only,  or  even  none  at  all; 
while  in  the  snakes  the  long,  slender,  cylindrical  body  is 
legless  or  at  most  has  mere  rudiments  of  the  hinder  limbs. 
With  the  reptiles  locomotion  is  as  often  effected  by  the 
bending  or  serpentine  movements  of  the  trunk  as  by  the 
use  of  legs.  Among  lizards  and  snakes  the  body  is 
covered  with  horny  epidermal  scales  or  plates,  while 


ELEMENTARY  ZOOLOGY 

among  the  turtles  and  crocodiles  there  may  be,  in  addition 
to  the  epidermal  plates,  a  real  deposit  of  bone  in  the  skin 
whereby  the  effectiveness  of  the  armor  is  increased.  The 
epidermal  covering  of  snakes  and  lizards  is  periodically 
molted,  or,  as  we  say,  the  skin  is  shed.  The  bright  colors 
and  patterns  of  snakes  and  of  many  lizards  are  due  to  the 
presence  and  arrangement  of  pigment-cells  in  the  skin. 
Among  some  reptiles,  notably  the  chameleons,  the  colors 
and  markings  can  be  quickly  and  radically  changed  by 
an  automatic  change  in  the  tension  of  the  skin. 

Structure. — In  reptiles,  as  in  batrachians,  the  chief 
variations  in  the  body  skeleton  are  correlated  with  differ- 
ences in  external  body  form.  In  the  short  compact  body 
of  the  turtles  and  tortoises  the  number  of  vertebrae  is  much 
smaller  than  in  the  snakes.  Some  turtles  have  only  34 
vertebrae;  certain  snakes  as  many  as  400.  The  reptilian 
skull,  in  the  number  and  disposition  of  its  parts  and  in  the 
manner  of  its  attachment  to  the  spinal  column,  resembles 
that  of  the  birds,  although  the  cranial  bones  remain  sep- 
arate, not  fusing  as  in  the  birds.  In  the  snake  the  two 
halves  of  the  lower  jaw  are  not  fused  in  front  but  are 
united  by  elastic  ligaments,  which  condition,  together 
with  the  extremely  mobile  articulation  of  the  base  of  the 
jaws,  allows  the  snakes  to  open  their  mouths  so  as  to  take 
in  bodies  of  great  size.  All  of  the  reptiles,  except  the 
turtles,  are  provided  with  small  teeth  which  serve,  gen- 
erally, for  seizing  or  holding  prey  and  not  for  mastication. 
The  poisonous  snakes  have  one  or  more  long,  sharp,  and 
grooved  or  hollow  fangs  (fig.  131).  In  the  legless  reptiles 
both  shoulder  and  pelvic  girdles  may  be  wholly  lacking; 
in  the  limbed  forms  both  girdles  are  more  or  less  well 
developed. 

The  tongue  of  many  reptiles,  notably  the  snakes,  is 
bifid  or  forked,  and  is  an  extremely  mobile  and  sensitive 
organ.  The  oesophagus  is  long  and  in  the  snakes  can  be 


'•        }    riT>"     -,^~--~^ 


1 


BRANCH  CHORD  AT  A:  CLASS  REPTILIA  3" 

stretched  very  wide  so  as  to  permit  the  swallowing  of 
large  animals  whole.  Reptiles  breathe  solely  by  lungs, 
of  which  there  is  a  pair  They  are  simple  and  sac-like, 
the  left  lung  being  often  much  smaller  than  the  other. 
In  turtles  and  crocodiles  the  lungs  are  divided  internally 
by  septa  into  a  number  of  chambers.  Because  of  the 
rigidity  of  the  carapace  or  "  box  "  of  turtles  the  air  cannot 
be  taken  in  the  ordinary  way  by  the  use  of  the  ribs  and 
rib-muscles,  but  has  to  be  swallowed.  The  reptilian  heart 
consists  of  two  distinct  auricles  and  of  two  ventricles, 
which  in  most  reptiles  are  only  incompletely  divided,  the 
division  into  right  and  left  ventricles  being  complete  only 
among  the  crocodiles  and  alligators,  the  most  highly 
organized  of  living  reptiles. 

The  organs  of  the  nervous  system  reach  a  considerable 
degree  of  development  in  the  animals  of  this  class.  The 
brain  in  size  and  complexity  is  plainly  superior  to  the 
batrachian  brain  and  resembles  quite  closely  that  of  birds. 
Of  the  organs  of  special  sense  those  of  touch  are  limited 
to  special  papillae  in  the  skin  of  certain  snakes  and  many 
lizards.  Taste  seems  to  be  little  developed,  but  olfactory 
organs  of  considerable  complexity  are  present  in  most 
forms,  and  consist  of  a  pair  of  nostrils  with  olfactory 
papillae  on  their  inner  surfaces.  The  ears  vary  much  in 
degree  of  organization,  crocodiles  and  alligators  being  the 
only  reptiles  with  a  well-defined  outer  ear.  This  consists 
of  a  dermal  flap  covering  a  tympanum.  Eyes  are  always 
present  and  are  highly  developed.  They  resemble  the 
eyes  of  birds  in  many  particulars.  All  reptiles,  excepting 
the  snakes  and  a  few  lizards,  have  movable  eyelids,  in- 
cluding a  nictitating  membrane  like  that  of  the  birds. 
With  the  snakes  the  eye  is  protected  by  the  outer  skin, 
which  remains  intact  over  it,  but  is  transparent  and 
thickened  to  form  a  lens  just  over  the  inner  eye.  Turtles 
and  lizards  have  a  ring  of  bony  plates  surrounding  the 


312  ELEMENTARY  ZOOLOGY 

eyes  similar  to  that  of  the  birds.  In  addition  to  the  usual 
eyes  there  is  in  many  lizards  a  remarkable  eye-like  organ, 
the  so-called  pineal  eye.  which  is  situated  in  the  roof  of 
the  cranium,  and  is  believed  to  be  the  vestige  of  a  true 
third  eye,  which  in  ancient  reptiles  was  probably  a  well- 
developed  organ. 

Life-history  and  habits. —Most  reptiles  lay  eggs  from 
which  the  young  hatch  after  a  longer  or  shorter  period  of 
incubation.  Usually  the  eggs  are  simply  dropped  on  the 
ground  in  suitable  places  (although  certain  turtles  dig 
holes  in  which  to  deposit  them),  where  they  are  incubated 
by  the  general  warmth  of  the  air  and  ground.  However, 
some  of  the  giant  snakes,  the  pythons  for  instance,  hold 
the  eggs  in  the  folds  of  the  body.  In  the  case  of  some 
snakes  and  lizards  the  eggs  are  retained  in  the  body  of 
the  mother  until  the  young  hatch;  such  reptiles  are  said 
to  be  ovoviviparous,  because  the  young,  although  born 
alive,  are  in  reality  enclosed  in  an  egg  until  the  moment 
of  birth.  Among  reptiles  the  newly  hatched  young 
resemble  the  parents  in  most  respects  except  in  size,  yet 
striking  differences  in  coloration  and  pattern  are  not  rare. 
But  there  is  in  this  class  no  metamorphosis  such  as 
characterizes  the  post-embryonic  development  of  the 
batrachians. 

The  food  of  reptiles  consists  almost  exclusively  of 
animal  substance,  although  some  species,  notably  the 
green  turtles  and  certain  land-tortoises,  are  vegetable- 
feeders.  The  animal-feeders  are  mostly  predaceous,  the 
smaller  species  catching  worms  and  insects,  while  the 
larger  forms  capture  fishes,  frogs,  birds,  and  their  eggs, 
small  mammals,  and  other  reptiles. 

Classification. — The  living  Reptilia  are  divided  into 
four  orders,  of  which  one  includes  only  a  single  genus, 
Hatterin,  a  peculiar  lizard  found  in  New  Zealand.  The 
other  three  are  the  Squamata,  which  includes  the  lizards 


BRANCH  CHORDATA:   CLASS  REPTIL1A  313 

and  snakes,*  distinguished  by  the  scaly  covering  of  the 
body,  the  Chelonia,  which  includes  the  tortoises  and 
turtles,  distinguished  by  the  shell  of  bony  plates  which 
encloses  the  body,  and  the  Crocodilia,  which  includes  the 
crocodiles  and  alligators,  whose  bodies  are  covered  with 
rows  of  sculptured  bony  scutes. 

Tortoises  and  turtles  (Chelonia). — TECHNICAL  NOTE.— 

Obtain  specimens  of  some  pond-  or  land-turtle  common  in  the 
vicinity  of  the  school.  The  red-bellied  and  yellow-bellied  terrapins 
(Pseudemys]  or  the  painted  or  mud-turtles  (Chrysemys]  are  com- 
mon over  most  of  the  United  States.  (Pseudemys  is  found  south  of 
the  Ohio  River  and  Chrysemys  north  of  it.)  They  may  be  raked 
up  from  creek-bottoms  or  fished  for  with  strong  hook  and  line, 
using  meat  as  bait.  They  will  live  through  the  winter  if  kept  in  a 
cool  place,  without  food  or  special  care  of  any  kind.  Observe  their 
swimming  and  diving,  the  retraction  of  head  and  limbs  into  the 
shell,  the  use  of  the  third  eyelid  (nictitating  membrane),  and  the 
swallowing  of  air. 

Examine  the  external  structure  of  a  dead  specimen  (kill  by 
thrusting  a  bit  of  cotton  soaked  with  chloroform  or  ether  into  the 
windpipe  ;  see  opening  just  at  base  of  tongue).  Note  shell  consist- 
ing of  a  dorsal  plate,  the  carapace,  and  ventral  plate,  the  plastron, 
and  the  lateral  uniting  parts,  the  bridge.  Note  legs,  and  head  with 
horny  beak  but  no  teeth.  Compare  with  snake.  The  examination 
of  the  internal  structure  of  the  turtle  can  be  readily  made  by  saw- 
ing through  the  bridge  on  either  side  and  removing  the  plastron. 
Note  the  ligaments  which  attach  the  plastron  to  the  shoulder  and 
pelvic  girdles.  Note  muscles  covering  these  bones.  Note  just 
behind  the  shoulder  girdle  the  heart  (perhaps  still  pulsating)  and 
the  dark  liver  on  each  side  of  it.  Work  out  the  alimentary  canal, 
the  trachea  and  lungs,  and  other  principal  organs,  comparing  them 
with  those  of  the  snake.  The  skeleton  can  be  studied  by  dissecting 
and  boiling  and  brushing  away  the  flesh  which  still  adheres  to  the 
bones.  The  comparison  of  the  skeleton  of  the  turtle  with  that  of 
the  snake  is  very  instructive  ;  marked  differences  in  the  skeletons  of 
the  two  kinds  of  reptiles  are  obviously  correlated  with  the  differ- 
ences in  habits  and  shape  of  body.  Note  in  the  skeleton  of  the 
turtle  especially  the  shoulder  and  pelvic  girdles  and  limbs  (absent  in 
the  snake)  and  small  number  of  vertebrae  and  ribs. 

Among  the  common  turtles  and  tortoises  of  the  United 
States  are  several  species  of  soft-shelled  turtles  (Trio- 

*  By  many  zoologists  the  lizards  and  snakes  are  held  to  form  two  distinct 
orders,  Lacertilia  and  Ophidia. 


314  ELEMENTARY  ZOOLOGY 

nychidae)  with  carapace  not  completely  ossified  and  both 
carapace  and  plastron  covered  by  a  thick  leathery  skin 
which  is  flexible  at  the  margins;  the  snapping-turtle 
(Chelydra  serpentind),  common  in  streams  and  ponds,  with 
shell  high  in  front  and  low  behind  and  head  and  tail  long 
and  not  capable  of  being  withdrawn  into  the  shell ;  the 
red-bellied  and  yellow-bellied  terrapins  (Pscudcmys),  red 
and  yellow,  with  greenish-brown  and  black  markings, 
common  on  the  ground  in  woods  and  among  rocks  and 
also  near  water  and  sometimes  in  it;  the  pond-  or  mud- 
turtle  (Chrysemys),  also  brightly  colored  and  usually  con- 
fined to  ponds  and  pond-shores;  and  the  box-tortoise 
(Cistudo  Carolina),  common  in  woods  and  upland  pastures 
and  readily  recognizable  by  its  ability  to  enclose  itself 
completely  in  its  shell  by  the  closing  down  of  the  lids 
of  the  plastron.  All  of  these  fresh-water  and  land-turtles 
except  the  soft-shelled  turtles  belong  to  one  family,  the 
Emydidae,  but  have  somewhat  diverse  habits.  Most  of 
them  are  carnivorous,  but  few  catch  any  very  active 
prey.  While  some  are  strictly  aquatic,  others  are  as 
strictly  terrestrial,  never  entering  the  water.  The  eggs 
of  all  are  oblong  and  are  deposited  in  hollows,  sometimes 
covered  in  sand.  The  newly  hatched  young  are  usually 
circular  in  shape,  and  vary  in  color  and  pattern  from  the 
parents. 

The  ' '  diamond-back  terrapin  ' '  (Malaclcmmys  pahis- 
tris),  used  for  food,  is  a  salt-water  form  "inhabiting  the 
marshes  along  the  Atlantic  coast  from  Massachusetts  to 
Texas.  About  Charleston  [and  Baltimore]  they  are 
very  abundant  and  are  captured  in  large  numbers  for 
market,  especially  at  the  breeding  season,  when  the 
females  are  full  of  eggs.  Further  north  they  are  dug 
from  the  salt  mud  early  in  their  hibernation  and  are 
greatly  esteemed,  being  fat  and  savory." 

Strongly  contrasting  with  the  usually  small  land-  and 


BRANCH  CHORD  AT  A:   CLASS  REPTIL1A 


315 


fresh-water  turtles  are  the  great  sea-turtles,  such  as  the 
leather-back,  the  loggerhead  and  the  green  turtles.  Some 
of  these  animals  reach  a  length  of  six  feet  and  more  and 
a  "weight  of  nine  hundred  pounds,  and  have  the  feet  com- 
pressed and  fin-shaped  for  swimming.  They  live  in  the 
open  ocean,  coming  on  land  only  to  lay  their  eggs,  which 
are  buried  in  the  sand  of  ocean  islands.  These  egg-laying 
visits  are  almost  always  made  at  night,  and  the  turtles 


FIG.  124.— The  giant  land-tortoise  of  the  Galapagos  Islands,  Testttdo  sp. 
These  tortoises  reach  a  length  of  four  feet.  (Photograph  from  life  by 
Geo.  Coleman.) 


are  then  often  caught  by  "turtlers."  The  flesh  of  most 
of  the  sea-turtles  is  used  for  food,  and  from  the  shell  of 
certain  species,  notably  the  "  hawk-bill  "  (Eretmochelys 
imbricatd]  the  beautiful  "tortoise-shell  "  used  for  making 
combs  and  other  articles  is  obtained.  The  common  green 
turtle  (Chclonia  my  das)  of  the  Atlantic  coast  is  the  species 
most  prized  for  food.  It  is  a  vegetarian,  feeding  on  the 
roots  of  Zostera,  the  plant  known  in  New  England  as 
eel-grass,  though  farther  south  it  is  called  turtle-grass. 


3l6  ELEMENTARY  ZOOLOGY 

When  grazing  the  turtles  eat  only  the  roots,  the  tops  thus 
rising  to  the  surface,  where  they  indicate  to  the  turtler  the 
animal's  whereabouts.  The  turtler,  armed  with  a  strong 
steel  barb  attached  to  a  rope  and  loosely  fitted  to  the  end 
of  a  pole,  carefully  rows  up  to  the  unsuspecting  animal, 
and  with  a  strong  thrust  plunges  the  barb  through  its 
shell,  withdraws  the  pole,  and,  grasping  the  rope,  now 
firmly  attached  to  the  turtle's  back,  lifts  the  animal  to  the 
surface.  Here,  with  assistance,  he  turns  it  into  the  boat, 
where  it  is  rendered  helpless  by  being  thrown  on  its  back 
and  by  having  its  flippers  tied.  These  turtles  are  also 
caught  on  their  breeding-gounds,  being  found  on  the  sand 
at  night  by  the  turtler,  turned  over  on  their  backs,  and 
left  thus  securely  caught  until  assistance  comes  to  help 
get  them  into  the  boats. 

Snakes  and  lizards  (Squamata). — TECHNICAL  NOTE.— A 

snake  has  already  been  dissected  and  studied.  It  will  be  instructive 
to  compare  the  external  structures,  at  least,  of  a  lizard  with  that  o. 
the  snake.  Specimens  of  some  species  of  the  common  swift  (Scelo- 
porus]  are  obtainable  almost  anywhere  in  the  United  States.  The 
"  pine-lizards  "  of  the  east  belong  to  this  genus.  Lizards  may  be 
sought  for  in  woods,  along  fences,  and  especially  on  warm  rocks. 


FIG.    125. — The    blue-tailed    skink,    Eumeces    skcltonianus.      (From    living 

specimen.) 

The  group  of  lizards  is  a  very  large  one,  about  1,500 
species  being  known,  but  it  is  represented  in  the  United 
States  by  comparatively  few  species.  Lizards  are  espe- 
cially abundant  in  the  tropics  of  South  America.  The 
strange  and  fantastic  appearance  presented  by  some  of 
them  has  made  certain  species  the  object  of  much  interest 


BRANCH  CHORD  AT  A  :   CLASS  REPTIL1A  3*7 

and  often  fear  on  the  part  of  the  natives  of  tropical  lands. 
In  those  regions  are  current  extraordinary  stories  and 
beliefs  regarding  the  habits  and  attributes  of  certain  lizards 
like  the  basilisk  and  chameleon.  Lizards  are  all  more  or 
less  elongate  and  some  are  truly  snake-like  in  form.  The 
legs,  though  usually  present  and  functional,  are  in  many 
cases  much  reduced,  and  in  some  forms,  as  the  glass- 
snake,  either  one  or  both  pairs  are  so  rudimentary  as  to 
have  no  external  projection  whatever.  Although  lizards 


FlG.    126. — The  Gila  monster,   Heloderma  horridum*    the   only  poisonous 
lizard.     (Photograph  from  life  by  J.  O.  Snyder. 

are  often  regarded  as  being  poisonous,  only  one  genus, 
Hcloderma,  the  Gila  Monster,  is  really  so.  All  others 
are  perfectly  harmless  as  far  as  poison  is  concerned,  and 
most  of  them  are  unusually  timid.  They  vary  in  size  from 
a  few  inches  to  six  feet  in  length.  Most  of  them  are  ter- 
restrial, some  arboreal,  and  some  aquatic. 

Among  the  lizards  of  this  country  the  swifts  and  ground- 
lizards  are  familiar  everywhere.  In  certain  regions  the 
glass-snake  or  joint-snake  (Opheosaurus  vcntralis)  is 
common.  This  animal,  popularly  considered  to  be  a 
snake,  has  no  external  limbs,  and  its  tail  is  so  brittle,  the 
vertebrae  composing  it  being  very  fragile,  that  part  of  it 
may  break  off  at  the  slightest  blow.  In  time  a  new  tail 
is  regenerated.  It  Jives  in  the  central  and  northern  part 
of  the  United  States,  and  burrows  in  dry  places.  In  the 
western  part  of  the  country  horned  toads  {Phrynosoma} 
are  common,  about  ten  different  species  being  known. 
These  are  lizards  with  shortened  and  depressed  body  and 
well-developed  legs.  The  body  is  covered  with  protec- 


3i8  ELEMENTARY  ZOOLOGY 

tive  spiny  protuberances,  and  in  individual  color  and 
pattern  resembles  closely  the  soil,  rocks,  and  cactus  among 
which  the  particular  horned  toad  lives.  All  the  species 
of  PJirynosoma  are  viviparous,  seven  or  eight  young  being 
born  alive  at  a  time, 

In  New  Mexico,  Arizona,  and  northern  Mexico  the  only 
existing  poisonous  lizards,  the  Gila  Monster  (Helodcrma) 
(fig.  126)  is  found.  This  is  a  heavy,  deep-black,  orange- 
mottled  lizard  about  sixteen  inches  long.  There  is  much 
variance  of  belief  among  people  regarding  the  Gila  Mon- 
ster, but  recent  experiments  have  proved  the  poisonous 
nature  of  the  animal.  The  poison  which  is  secreted  by 
glands  in  the  lower  jaw  flows  along  the  grooved  teeth  into 
the  wound.  A  beautiful  and  interesting  little  lizard  found 
in  the  South  is  the  green  chameleon  (Anolis  principalis}. 
Its  body  is  about  three  inches  long  with  a  slender  tail  of 
five  or  six  inches.  The  normal  color  of  the  chameleon  is 
grass-green,  but  it  may  "assume  almost  instantly  shades 
varying  from  a  beautiful  emerald  to  a  dark  and  iridescent 
bronze  color. " 

In  the  tropics  many  of  the  lizards  reach  great  size  and 
are  of  strange  shape  and  patterns.  The  flying  dragons 
(Draco]  have  a  sort  of  parachute  on  each  side  of  the  body 
composed  of  a  fold  of  skin  supported  by  five  or  six  false 
.posterior  ribs.  These  lizards  live  in  the  trees  of  the  East 
Indies  and  "fly"  or  sail  from  tree  to  tree.  They  are 
very  beautifully  colored.  The  iguanas  (Iguana)  of  the 
tropics  of  South  America  are  commonly  used  for  food. 
They  live  mostly  in  trees,  and  reach  a  length  of  five  or 
six  feet.  The  monitor  ( Varanus  niloticus)  is  a  great 
water-lizard  that  lives  in  the  Nile,  and  feeds  on  crocodiles' 
eggs>  of  which  it  destroys  great  numbers.  It  is  the  prin- 
cipal enemy  of  the  crocodile.  When  full  grown  it  reaches 
a  length  of  six  feet  or  even  more. 

About    1,000    living    species    of   snakes    are     known.. 


BRANCH  CHORD  AT  A:   CLASS  REPTILIA  319 

Usually  they  have  the  body  regularly  cylindrical,  and 
without  distinct  division  into  body  regions.  Legs  are 
wanting,  locomotion  being  effected  by  the  help  of  the 
scales  and  the  ribs.  No  snake  can  move  forward  on  a 
perfectly  smooth  surface  and  no  snake  can  leap.  In  some 
forms,  such  as  the  pythons,  external  rudiments  of  the  hind 
limbs  are  present,  but  do  not  aid  in  locomotion.  The 
mouth  is  large  and  distensible  so  that  prey  of  considerably 
greater  size  than  the  normal  diameter  of  the  snake's  body 
is  frequently  swallowed  whole.  The  sense  of  taste  is  very 
little  if  at  all  developed,  as  the  food  is  swallowed  without 
mastication.  The  tongue,  which  is  protrusible  and  usually 
red  or  blue-black,  serves  as  a  special  organ  of  touch. 
Hearing  is  poor,  the  ears  being  very  little  developed. 
The  sense  of  sight  is  also  probably  not  at  all  keen. 
Snakes  rely  chiefly  on  the  sense  of  smell  for  finding  their 
prey  and  their  mates.  The  colors  of  snakes  are  often 
brilliant,  and  in  many  cases  serve  to  produce  an  effective 
protective  resemblance  by  harmonizing  with  the  usual 
surroundings  of  the  animal.  The  food  of  snakes  consists 
almost  exclusively  of  other  animals,  which  are  caught 
alive.  Some  of  the  poisonous  snakes  kill  their  prey  before 
swallowing  it,  as  do  some  of  the  constrictors.  While  most 
snakes  live  on  the  ground,  some  are  semi-arboreal  and 
others  spend  part  or  all  of  their  time  in  water.  Cold- 
region  snakes  spend  the  winter  in  a  state  of  suspended 
animation  ;  in  the  tropics,  on  the  contrary,  the  hottest  part 
of  the  year  is  spent  by  some  species  in  a  similar  * '  sleep. ' ' 
There  are  so  many  common  snakes  in  the  United  States 
that  only  a  few  of  the  more  familiar  forms  can  be  men- 
tioned. The  non-poisonous  species  of  America  belong 
to  the  family  Colubridae,  while  all  but  one  of  the  poisonous 
species  belong  to  the  family  Crotalidre,  characterized  by 
the  presence  of  a  pair  of  erectile  poison-fangs  on  the  upper 
jaw.  Among  the  commonest  of  the  Colubridae  are  the 


320  ELEMENTARY  ZOOLOGY 

garter  snakes  (ThatnnopJiis)  (fig.  127),  always  striped  and 
not  more  than  three  feet  long.  The  most  widespread 
species  is  Thamnophis  sirtalis,  rather  dully  colored  with 
three  series  of  small  dark  spots  along  each  side.  The 


FlG.  127. — A  garter  snake,   Thamnophis  parietalis.     (Photograph  from  life 
by  J.  O.  Snyder.) 

common  water-snake  (Natrix  sipedon)  is  brownish  with 
back  and  sides  each  with  a  series  of  about  80  large  square 
dark  blotches  alternating  with  each  other.  It  feeds  on 
fishes  and  frogs,  and  although  "  unpleasant  and  ill-tem- 
pered "  is  harmless.  One  of  the  prettiest  and  most  gentle 
of  snakes  is  the  familiar  little  greensnake  (Cyclophis 
cestivus},  common  in  the  East  and  South  in  moist 
meadows  and  in  bushes  near  the  water.  It  feeds  on  in- 
sects and  can  be  easily  kept  alive  in  confinement.  A 
familiar  larger  snake  is  the  blacksnake  or  blue  racer  (Bas- 
caniom  constrictor^},  ''lustrous  pitch  black,  general  color 
greenish  below  and  with  white  throat."  It  is  "often 
found  in  the  neighborhood  of  water,  and  is  particularly 
partial  to  thickets  of  alders,  where  it  can  hunt  for  toads, 
mice,  and  birds,  and  being  an  excellent  climber  it  is  often 
seen  among  the  branches  of  small  trees  and  bushes, 
hunting  for  young  birds  in  the  nest."  The  chain-snake 
(Lampropeltis  getulus)  of  the  southeast  and  the  king- 
snake  (also  a  Lampropeltis)  (fig.  128)  of  the  central 


BRANCH  CHORD  AT  A:   CLASS  REPTILIA 


States  are  beautiful  lustrous  black-and-yellow  spotted 
snakes  which  feed  not  only  on  lizards,  salamanders, 
small  birds  and  mice  but  also  on  other  snakes.  The 
king-snake  should  be  protected  in  regions  infested  by 
"rattlers."  The  spreading  adder  or  blowing  viper 
(Heterodox  platirhinos],  a  common  snake  in  the  eastern 
States,  brownish  or  reddish  with  dark  dorsal  and  lateral 
blotches,  depresses  and  expands  the  head  when  angry, 
hissing  and  threatening.  Despite  the  popular  belief  in  its 
poisonous  nature  this  ugly  reptile  is  quite  harmless.  It 
specially  infests  dry  sandy  places. 

With  the  exception  of  the  coral  or  beadsnake  (Elaps 
fulvius],  a  rather  small  jet-black  snake  with  seventeen 
broad  yellow-bordered  crimson  rings,  found  in  the 
southern  States,  the  only  poisonous  snakes  of  the  United 
States  are  the  rattlesnakes  and  their  immediate  relatives, 
the  copperhead  and  water-moccasin.  These  snakes  all 
have  a  large  triangular  head,  and  the  posterior  tip  of  the 
body  is,  in  the  rattlesnakes,  provided  with  a  "rattle" 


FlG.  128. — A  king-snake,   Lampropeltis  boy  Hi. 
J.  O.  Snyder.) 


(Photograph  from  life  by 


composed  of  a  series  of  partly  overlapping  thin  horny 
capsules  or  cones  of  shape  as  shown  in  figure  130.  These 
horny  pieces  are  simply  the  somewhat  modified  succes- 
sively formed  epidermal  coverings  of  the  tip  of  the  body, 


322  ELEMENTARY  ZOOLOGY 

which  instead  of  being  entirely  molted  as  the  rest  of  the 
skin  is,  are,  because  of  their  peculiar  shape,  loosely  attached 
to  one  another,  and  by  the  basal  one  to  the  body  of  the 
snake.  The  number  of  rattles  does  not  correspond  to  the 
snake's  years  for  several  reasons,  partly  because  more 
than  one  rattle  can  be  added  to  the  tail  in  a  year,  and 
especially  because  rattles  are  easily  and  often  broken  off. 
As  many  as  thirty  rattles  have  been  found  on  one  snake. 
There  are  two  species  of  ground-rattlesnakes  or  massa- 


FlG.   129. The  gopher-snake.    Pituophis  bellona.      ^Photograph    from  life 

by  J.  O.  Snyder.) 


saugas  (Sistrurns)  in  the  United  States  and  ten  species  of 
the  true  rattlesnakes  (Crotalus).  The  centre  of  distribu- 
tion of  the  rattlesnakes  is  the  dry  tablelands  of  the  south- 
west in  New  Mexico,  Arizona,  and  Texas.  But  there  are 
few  localities  in  the  United  States  outside  the  high  moun- 
tains in  which  "rattlers  "  do  not  occur  or  did  not  occur 
before  they  were  exterminated  by  man.  The  copperhead 
(Agkistrodon  contortix)  is  light  chestnut  in  color,  with 
inverted  Y-shaped  darker  blotches  on  the  sides,  and 


BRANCH   CHORDATA:   CLASS  REPTIL1A  323 

seldom  exceeds  three  feet  in  length.  It  occurs  in  the 
eastern  and  middle  United  States  from  Pennsylvania  and 
Nebraska  southward.  It  is  a  vicious  and  dangerous 
snake,  striking  without  warning.  The  water-moccasin 
(Agkistrodon  piscivorous]  is  dark  chestnut-brown  with 
darker  markings.  The  head  is  purplish  black  above. 
It  is  found  along  the  Atlantic  and  Gulf  coasts  from  North 
Carolina  to  Mexico,  extending  also  some  distance  up  the 
Mississippi  valley.  It  is  distinctively  a  water-snake,  being 
found  in  damp  swampy  places  or  actually  in  water.  It 
reaches  a  length  of  over  four  feet  and  is  a  very  venomous 
snake,  striking  on  the  slightest  provocation.  The  com- 
mon harmless  water-snake  is  often  called  water-moccasin 
in  the  southern  States,  being  popularly  confounded  with 
this  most  dangerous  of  our  serpents.  The  poison  of  all  of 
these  snakes  is  a  rather  yellowish,  transparent,  sticky  fluid 
secreted  by  glands  in  the  head,  from  which  it  flows  through 


FIG.  130. — The  rattles  of  the  rattlesnake;  the  lower  figure  shows  a  longi 
tudinal  section  of  the  rattle. 


the  hollow  maxillary  fangs.  The  character  and  position 
of  the  fangs  are  shown  in  figure  131.  Remedial  measures 
for  the  bite  of  poisonous  snakes  are,  first,  to  stop,  if  possi- 
ble, the  flow  of  blood  from  the  wound  to  the  heart,  by 


324  ELEMENTARY  ZOOLOGY 

compressing  the  veins  between  the  wound  and  heart,  then 
to  suck  (if  the  lips  are  unbroken)  the  poison  from  the 
wound,  next  to  introduce  by  hypodermic  injection  per- 
manganate of  potash,  bichloride  of  mercury  or  chromic 
acid  into  the  wound,  and  finally  perhaps  to  take  some 
strong  stimulant  as  brandy  or  whiskey. 

Of  the  kinds  of  snakes  not  found  in  this  country  perhaps 
the  most  interesting  are  the  gigantic  boa  constrictors, 
anacondas,  and  pythons.  Pythons  are  found  in  India, 
the  islands  of  the  Malay  archipelago,  and  Australia,  while 
the  boas  and  anacondas  live  in  the  tropics  of  America. 
The  largest  pythons  reach  a  length  of  thirty  feet  and  some 
of  the  boas  are  nearly  as  large.  These  snakes  feed  on 


FIG.  131. — Dissection  of  head  of  rattlesnake;  /,  poison-fangs;  /,  poison-sac. 


small  mammals  such  as  fawns,  kids,  water-rats,  etc.,  and 
birds.  The  prey  is  swallowed  whole,  being  first  encircled 
and  crushed  to  death  in  folds  of  the  body.  After  a  meal 
the  python  or  boa  lies  in  a  sort  of  torpor  for  some  time. 
A  famous  snake  is  the  deadly  cobra-da-capello  of  India. 
These  snakes  are  so  abundant  and  the  bite  is  so  nearly 
certainly  fatal  that  thousands  of  persons  are  killed  each 
year  in  India  by  it.  Other  extremely  poisonous  snakes 
are  the  vipers  ( Vipera  cerastes),  which  live  in  the  hot 
deserts  of  northern  Africa.  Over  each  eye  there  is  a  scaly 


BRANCH  CHORD  AT  A:   CLASS  REP  Jill  A  325 

spine  or  horn,  from  which  the  name  horned  viper  is 
derived.  The  most  poisonous  snake  of  South  Africa  is 
the  large  and  ugly  puff-adder,  which  puffs  itself  up  when 
irritated.  An  interesting  group  of  snakes  is  that  of  the 
Hydrophidse  or  sea-snakes,  which  swim  on  the  surface  of 
the  ocean  by  means  of  their  flattened  and  oar-like  tails. 
These  forms  live  in  the  tropical  portions  of  the  Indian  and 
Pacific  oceans,  ranging  as  far  north  as  the  Gulf  of  Cali- 
fornia, and  spend  their  whole  life  in  the  water,  "out  of 
which  they  appear  to  be  blind  and  soon  die."  They  are 
extremely  venomous,  but  are  all  of  small  size,  rarely  two 
feet  long. 

Crocodiles  and  alligators  (Crocodilia) . — The  crocodiles 
and  alligators  are  reptiles  familiar  by  name  and  appear- 
ance, though  seen  in  nature  only  by  inhabitants  or  visitors 
in  tropical  and  semitropical  lands.  In  the  United  States 
there  are  two  species  of  these  great  reptiles,  the  American 
crocodile  (Crocodilns  americanus],  living  in  the  West 
Indies  and  South  America  and  occasionally  found  in 
Florida,  and  the  American  alligator  (Alligator  missis- 
sippiensis)^  common  in  the  morasses  and  stagnant  pools 
of  the  southern  States.  The  alligator  differs  from  the 
crocodiles  in  having  a  broader  snout.  It  is  rarely  more 
than  twelve  feet  long.  The  best-known  crocodile  is  the 
Nile  crocodile,  which  is  not  limited  to  the  Nile,  but  is 
found  throughout  Africa.  In  the  Ganges  of  India  is 
found  another  member  of  this  group. of  reptiles  called  the 
gavial.  It  is  among  the  largest  of  the  order,  reaching  a 
length  of  twenty  feet.  The  crocodiles,  alligators,  and 
gavials  comprise  not  more  than  a  score  of  species 
altogether,  but  because  of  their  wide  distribution,  great 
size,  and  carnivorous  habits  they  are  among  the  most 
conspicuous  of  the  larger  living  animals.  They  live  mostly 
in  the  water,  going  on  land  to  sun  themselves  or  to  lay 
their  eggs.  They  move  very  quickly  and  swiftly  in  water 


326  ELEMENTARY  ZOOLOGY 

but  are  awkward  on  land.  Fish,  aquatic  mammals  and 
other  animals  which  occasionally  visit  the  water  are  their 
prey.  The  gavial  and  Nile  crocodile  are  both  known  to 
attack  and  devour  human  beings,  and  these  species 
annually  cause  a  considerable  loss  of  life.  But  few  such 
fatalities,  however,  are  accredited  to  the  American  alli- 
gator. 


CHAPTER    XXVII 

BRANCH  CHORDATA  (Continued}.     CLASS  AVES: 
THE    BIRDS 

THE   ENGLISH    SPARROW  (Passer  domesticus} 

TECHNICAL  NOTE. — The  English  sparrow  may  be  found  now  in 
cities  and  villages  all  over  the  United  States.  It  has  become  a 
veritable  pest,  and  the  killing  of  the  few  needed  for  the  laboratory 
may  be  looked  pn  as  desirable  rather  than  deplorable,  as  is  the 
killing  of  birds  in  almost  all  other  cases.  The  males  have  a  black 
throat,  with  the  other  head-markings  strong  and  contrasting  (black, 
brown,  and  white),  while  the  females  have  a  uniform  grayish  and 
brownish  coloration  on  the  head. 

Specimens  are  best  taken  alive,  as  shooting  usually  injures  them 
for  dissection.  One  can  rely  on  the  ingenuity  of  the  boys  of  the 
class  to  procure  a  sufficient  number  of  specimens.  Observations 
on  the  habits  of  the  birds  should  be  made  by  the  pupils  as  they  go 
to  and  from  school.  For  dissection  use  fresh  specimens  if  possible. 
If  desirable  a  pigeon  or  dove  may  be  used  in  place  of  the  sparrow. 

External  structure. — Note  in  the  sparrow  the  same 
general  arrangement  of  body  parts  as  in  the  toad,  the 
body  being  divided  into  head,  upper  limbs,  trunk,  and 
lower  limbs.  In  the  toad,  however,  all  of  the  limbs  are 
fitted  for  walking  and  jumping,  whereas  in  the  sparrow  the 
anterior  pair  of  appendages,  the  wings,  are  modified  to 
be  organs  of  flight,  and  the  posterior  limbs  are  specially 
adapted  for  perching.  Note  that  the  sparrow  is  covered 
with  feathers,  some  long,  some  short,  in  some  places  thick 
and  in  others  thin,  but  all  fitting  together  to  form  a  com- 
plete covering  for  the  body.  Note  also  that  the  anterior 
end  of  the  head  is  prolonged  into  a  hard  bony  structure, 

327 


328  ELEMENTARY  ZOOLOGY 

the  bill)  covered  with  horny  substance.  This  horny  sub- 
stance together  with  the  feathers  and  horny  covering  of 
the  feet  are  modified  portions  of  the  skin.  Note  the  long 
quill-feathers  attached  to  the  posterior  edge  of  the  wing. 
By  these  the  bird  sustains  its  flight.  Other  long  quill- 
feathers  are  attached  to  the  posterior  end  of  the  body, 
forming  the  tail.  By  a  system  of  muscles  connected  with 
these  feathers  they  act  together,  serving  as  a  rudder  during 
flight  and  as  a  balancing  contrivance  when  perching. 
Note  just  above  the  bill  two  openings  protected  by  tufts 
of  feathers.  What  are  these  openings  ?  How  are  they 
connected  with  the  moutli  f  Note  the  large  eyes,  and  at 
the  inner  angle  of  each  the  delicate  nictitating  membrane 
which  can  be  drawn  over  the  ball.  Does  the  bird  have 
external  ears  ?  Lift  the  feathers  just  above  the  tail  (the 
upper  tail-coverts)  and  note  a  small  median  gland,  the 
oil-gland,  from  which  the  bird  derives  the  oil  with  which 
it  oils  its  feathers.  Beneath  the  tail  note  the  opening 
from  the  alimentary  canal  and  from  the  kidneys  and 
reproductive  organs.  This  is  called  the  cloaca!  opening. 

Examine  in  detail  some  of  the  feathers.  In  one  of  the 
quill-feathers  note  the  central  stem  or  shaft  composed  of 
two  parts,  a  basal  hollow  quill,  which  bears  no  web  and 
by  which  the  feather  is  inserted  in  the  skin,  and  a  longer, 
terminal,  four-sided  portion,  the  rachis,  which  bears  on 
either  side  a  web  or  vane.  Each  vane  is  composed  of 
many  narrow  linear  plates,  the  barbs,  from  which  rise 
(like  miniature  vanes)  many  barbules.  Each  barbule 
bears  many  fine  barbicels  and  hamuli  or  hooklets.  The 
barbs  of  the  feather  are  interlocked.  How  is  this  effected  ? 
The  feathers  which  overlie  the  whole  body  and  bear  the 
color  pattern  are  called  contour -feathers.  How  do  they 
differ  from  or  correspond  with  the  quill-feathers  in  struc- 
ture ?  Soft  feathers  called  down-feathers,  or  plumules, 
cover  the  body  more  or  less  completely,  being,  however, 


BRANCH  CHORD  AT  A;   CLASS  AVES:   THE  BIRDS      329 

mostly  hidden  by  the  contour-feathers ;  the  barbs  of  these 
are  sometimes  not  borne  on  a  rachis,  but  arise  as  a  tuft 
from  the  end  of  the  quill.  Certain  other  feathers  which 
have  an  extremely  slender  stem  and  usually  no  vane, 
except  a  small  terminal  tuft  of  barbs,  are  called  thread- 
feathers,  or  filoplumules.  They  are  rather  long,  but  are 
mostly  hidden  by  the  contour-feathers.  In  certain  birds 
they  stand  out  conspicuously,  as  the  vibrissce  about  the 
nostrils. 

In  the  determination  of  birds  by  the  use  of  a  classifica- 
tory  "key"  (see  p.  359  it  is  necessary  to  be  familiar 
with  the  names  applied  to  the  various  external  regions  of 
the  body  and  plumage,  and  with  the  terms  used  to  denote 
the  special  varying  conditions  of  these  parts.  By  refer- 
ence to  figure  133  the  names  of  the  regions  or  parts  most 
commonly  referred  to  may  be  learned.  A  full  account 
of  all  of  the  external  characters  with  definitions  of  the 
various  terms  used  in  referring  to  them  may  be  found  in 
Coues's  "  Key  to  North  American  Birds." 

TECHNICAL  NOTE.—  Pull  the  feathers  from  the  body,  being  care- 
ful not  to  tear  the  skin. 

In  the  fish  and  toad,  already  studied,  the  head  is  closely 
joined  to  the  trunk.  How  is  it  with  the  bird  ?  Observe 
that  the  knee  of  the  sparrow  is  covered  by  feathers  and 
that  it  is  the  ankle  which  extends  down  as  the  bare  un- 
feathered  part  to  the  digits.  How  many  digits  have  the 
feet  of  the  bird  ?  How  are  they  arranged  ? 

Internal  structure  (fig.  132). — TECHNICAL  NOTE.— With  a 

pair  of  scissors  cut  just  beneath  the  skin  anteriorly  from  the  cloacal 
opening  to  the  angle  of  the  lower  jaw.  Pin  the  sparrow  on  its  back 
by  the  wings,  feet,  and  bill.  Push  back  the  skin  from  both  sides 
and  pin  out. 

Note  the  large  powerful  pectoral  muscles.  Note  a  hard 
median  projection  of  bone,  the  stern urn,  which  is  a  large 


33° 


ELEMENTARY  ZOOLOGY 


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BRANCH  CHORD  AT  A;   CLASS  AYES:    THE  BIRDS      331 

keel-shaped  bone  with  lateral  expansions  to  which  are 
attached  the  ribs.  Where  are  the  largest  and  most 
powerful  muscles  of  the  toad  located  ?  Where  are  they 
in  the  fish  ?  In  the  bird  the  most  powerful  muscles  are 
these  pectoral  muscles,  which  move  the  wings  in  flight. 

TECHNICAL  NOTE. — Cut  the  pectoral  muscles  from  the  left  side 
of  the  sternum,  push  hack  and  pin  to  one  side.  With  a  strong  pair 
of  scissors  cut  through  the  ribs  on  the  left  side  of  the  sternum  and 
through  the  overlying  bones.  Lift  the  whole  sternum,  with  the 
right  pectoral  muscle  attached,  to  the  left  side  of  the  pan  and  pin  it 
down.  Cut  through  the  membrane  which  covers  the  viscera  and 
cover  the  dissection  with  water. 

In  this  operation  note  the  V-shaped  wishbone  in  front 
of  the  sternum.  It  is  composed  of  the  two  clavicles  with 
their  inner  ends  fused.  Note  the  stout  coracoid  bones 
extending  from  the  anterior  end  of  the  sternum  to  the 
shoulder. 

Note  near  the  middle  of  the  body  the  heart  with  the 
large  blood-vessels  proceeding  from  it.  Behind  the  heart 
lies  the  large  reddish-brown  liver,  and  on  the  left  side 
below  the  liver  is  the  large  gizzard  or  muscular  stomach. 
Note  the  viscera  folded  over  themselves  in  the  body- 
cavity.  Push  them  temporarily  aside  and  note  in  the 
dorsal  region  under  the  heart  large  pinkish  spongy  sacs, 
the  lungs.  These  are  attached  by  short  tubes,  the 
bronchi,  to  the  long  cartilaginous  trachea.  At  the  union 
of  the  bronchi  with  the  trachea  is  a  small  expansion  with 
cartilaginous  walls,  writhin  which  are  stretched  small  bands 
of  muscles.  This  organ  is  the  syrinx,  the  song-  or  voice- 
apparatus  of  the  bird.  It  should  be  cut  open  and  carefully 
examined.  Trace  the  trachea  fonvard  to  its  anterior  end. 
It  opens  by  a  glottis  into  the  larynx,  a  slightly  swollen 
chamber  with  cartilaginous  walls.  Note  the  U-shaped 
hyoid  bone  surrounding  the  front  of  the  glottis.  Through 
a  blowpipe  or  quill  inserted  into  the  glottis  blow  air  into 
the  .trachea  and  observe  the  inflation  of  the  lungs  and  of 


332  ELEMENTARY  ZOOLOGY 

certain  large  air-sacs  in  the  abdomen,  which  communicate 
with  them. 

Beneath  the  trachea  note  the  long  oesophagus.  Inflate 
the  oesophagus  with  a  blowpipe  and  note  how  distensible 
is  its  lower  end  near  the  breast.  This  distensible  portion 
is  called  the  crop.  If  the  alimentary  canal  be  drawn  out 
straight  the  oesophagus  will  be  found  to  run  as  an  almost 
straight  tube  down  the  left  side  of  the  body  to  the  gizzard. 
This  latter  organ  has  very  thick  muscular  walls  and  in  it 
the  food  is  ground  up  among  the  small  bits  of  gravel  it 
contains.  Extending  from  the  gizzard  near  the  entrance 
of  the  oesophagus  note  the  long  pyloric  loop  of  the  intes- 
tine called  duodenum.  Within  this  loop  is  a  long  pinkish 
gland,  the  pancreas,  which  empties  by  a  duct  into  the 
duodenum.  Into  the  duodenum  also  the  overlying  liver 
empties  its  secretion  of  bile  from  the  median-placed  gall- 
bladder. From  the  duodenum  the  small  intestine  or  ileum 
extends  with  many  convolutions  to  its  exit  through  the 
cloacal  aperture.  On  the  intestine  near  the  cloaca!  open- 
ing note  a  pair  of  glandular  structures,  the  cceca.  The 
short  part  of  intestine  between  the  caeca  and  cloaca  is 
called  the  rectum.  On  the  left  side  of  the  body  beneath 
the  gizzard  note  a  dark  glandular  structure,  the  spleen. 

Make  a  drawing  of  the  dissection  as  so  far  worked  out. 

TECHNICAL  NOTE  — Remove  the  alimentary  canal,  cutting  it  free 
posteriorly  at  the  caeca  and  anteriorly  just  above  the  muscular  gizzard. 
Cut  open  the  gizzard  and  note  its  structure.  The  contained  sand 
and  gravel  grains  are  picked  up  by  the  bird  as  it  eats. 

On  either  side  of  the  throat  note  the  well-defined  thyroid 
gland ;  in  young  sparrows  will  be  noted  on  each  side  cf 
the  neck  a  mass  of  tissue,  the  remains  of  the  thymus 
gland,  which  disappears  in  the  adult. 

Cut  transversely  through  the  lower  end  of  the  heart  and 
note  that  the  ventricles  are  wholly  distinct,  whereas  in  the 
toad  and  snake  they  are  incompletely  separated  In  the 


BRANCH  CHORDATA;   CLASS  AYES:    THE  BIRDS       333 

bird  there  is  a  complete  double  circulation.  Its  blood  is 
not  mixed,  the  pure  with  the  impure,  as  in  the  toad  and 
snake.  Blood  passing  through  the  right  auricle  and  i'cn- 
triclc goes  to  the  lungs;  on  its  return  to  the  heart  purified, 
it  enters  the  left  auricle  and  left  ventricle,  thence  to  pass 
out  over  the  body  through  the  arteries. 

Note  the  large  corta  given  off  from  the  left  ventricle. 
Note  the  two  large  branches,  the  innominate  arteries, 
given  off  by  it  near  its  origin.  Each  innominate  divides 
into  three  smaller  arteries,  a  carotid,  branchial,  and  pec- 
toral. The  aorta  itself  turns  toward  the  back  and  con- 
tinues posteriorly  through  the  body  as  the  dorsal  aorta. 
To  the  right  auricle  come  three  large  veins,  the  right  and 
left  pracavce  and  the  postcava.  Each  praecava  is  formed 
by  three  veins,  faejugvlar  from  the  head,  the  branchial 
from  the  wing,  and  the  pectoral  from  the  pectoral  muscles. 
The  postcava  comes  from  the  liver.  From  the  right 
ventricle  go  the  short  right  and  left  pulmonary  arteries 
to  the  lungs,  and  from  the  lungs  the  blood  is  brought  to 
the  left  auricle  through  the  right  and  left  pulmonary  veins. 

TECHNICAL  NOTE. — For  a  detailed  study  of  the  circulation  of 
the  bird  the  teacher  should  inject  the  blood  system  of  some  larger 
bird,  as  a  pigeon  or  fowl,  for  a  class-demonstration.  (For  a  guide, 
use  Parker's  "  Zootomy,"  p.  209,  or  Martin  and  Moale's  "  How  to 
Dissect  a  Bird,"  pp.  135-140  and  pp.  148,  149.) 

In  the  posterior  dorsal  region  of  the  body-cavity  will 
be  found  large  three-lobed  organs  fitting  into  the  spaces  be- 
tween the  bones  of  the  back  on  either  side.  These  are  the 
kidneys,  and  from  their  outer  margins  on  each  side  a  ureter 
runs  posteriorly  into  the  cloaca.  Overlying  the  anterior 
ends  of  the  kidneys  are  the  reproductive  organs.  In  the 
male  these  glands  consist  of  firm,  whitish,  glandular 
bodies.  From  each  runs  a  long  convoluted  i>as  defcrens, 
which  enters  the  cloaca.  This  tube  corresponds  to  the 
egg-duct  of  the  female.  In  the  female  the  right  egg- 


334  ELEMENTARY  ZOOLOGY 

glandzi\<\  egg-duct  or  oviduct  are  wanting.  The  left  egg- 
gland  appears  as  a  glandular  mass;  during  the  breeding 
season  yellow  ova  or  eggs  in  various  stages  of  develop- 
ment project  from  its  surface.  The  oviduct  opens  by  a 
funnel-shaped  mouth  near  the  egg-gland  and  runs  thence 
to  the  cloaca.  The  eggs  pass  from  the  egg-gland  into  the 
body-cavity,  where  they  are  caught  in  the  upper  end  of 
the  oviduct  and  carried  down  and  out  through  the  cloacal 
opening.  It  is  in  the  oviduct  that  the  egg  derives  its 
accessory  covering,  which  consists  of  a  white  or  albumin- 
ous portion,  together  with  several  enveloping  membranes 
and  the  hard  shell  enclosing  all. 

Remove  the  top  of  the  skull  and  note  the  large  brain. 
What  portions  of  the  brain  make  up  the  greater  part  of 
it  ?  Note  the  differences  between  this  brain  and  that  of 
the  toad.  Trace  the  principal  cranial  nerves.  Work  out 
the  spinal  cord  and  principal  spinal  nerves.  For  an 
account  of  the  nervous  system  of  the  sparrow  see  Martin 
and  Moale's  "How  to  Dissect  a  Bird,"  pp.  150-163. 

TECHNICAL  NOTE. — For  a  study  of  the  skeleton  of  the  sparrow 
a  specimen  should  be  cleaned  by  boiling  in  a  soap-solution  (see  p. 
452). 

In  the  sparrow's  skeleton  note  the  compactness  of  the 
skull  and  the  fusion  of  its  bones.  Observe  the  long 
cervical  vertebra  which  support  the  skull,  also  the 
thoracic  vertebrce  bearing  the  ribs  and  sternum.  How 
many  of  each  of  these  kinds  of  vertebrae  are  there  ?  The 
vertebrae  posterior  to  the  thorax  are  more  or  less  fused 
together  to  form  "the  sacrum,  which,  with  the  pelvic  girdle, 
supports  the  leg-bones.  The  bones  of  the  tail  consist  of 
a  number  of  very  small  vertebrae,  some  of  which  are  fused 
together.  Note  the  correspondence  between  the  bones 
of  the  leg  and  those  of  the  wing.  What  are  the  names 
of  each  of  the  bones  of  each  limb,  and  what  are  the  corre- 
sponding bones  in  the  two  limbs  ?  The  wings  and  legs 


BRANCH  CHORD  AT  A ;   CLASS  AVES  :    THE  BIRDS       335 

being  modified  for  different  uses,  their  various  bones  have 
assumed  different  relations  to  each  other  and  to  the  body, 
for  they  are  bent  at  directly  opposite  angles  and  the 
attachment  of  muscles  is  different.  Compare  the  skeleton 
of  the  bird  with  that  of  the  toad.  (For  a  detailed  account 
of  the  skeleton  of  the  bird  see  Parker's  "  Zootomy, " 
pp.  182-209,  or  Martin  and  Moale's  "  How  to  Dissect  a 
Bird,"  pp.  102-125.) 

Life-history  and  habits. — The  English  sparrow  was 
first  introduced  into  the  United  States  in  1850,  and  since 
that  time  has  rapidly  populated  most  of  the  cities  and 
towns  of  the  country.  On  account  of  its  extreme  adapt- 
ability to  surroundings,  its  omnivorous  food-habits  and  its 
fecundity  it  survives  where  other  birds  would  die  out. 
It  also  crowds  out  and  has  caused  the  disappearance  or 
death  of  other  birds  more  attractive  and  more  useful. 
The  sparrow  annually  rears  five  or  six  broods  of  young, 
laying  from  six  to  ten  eggs  at  each  sitting.  Had  it  no 
enemies  a  single  pair  of  sparrows  would  multiply  to  a 
most  astonishing  number.  The  sparrow  has,  however,  a 
number  of  enemies,  most  common  among  them  perhaps 
being  the  "  small  boy,"  but  birds  and  mammals  play  the 
chief  part  in  the  destruction.  The  smaller  hawks  prey 
upon  them,  and  rats  and  mice  destroy  great  numbers  of 
their  young  and  of  their  eggs  whenever  the  nests  can  be 
reached.  The  sparrow  is  omnivorous  and  when  driven 
to  it  is  a  loathsome  scavenger,  though  at  other  times  its 
tastes  are  for  dainty  fruits.  Its  senses  of  perception  are 
of  the  keenest;  it  can  determine  friend  or  foe  at  long 
range.  The  nesting  habits  are  simple,  the  nests  being 
roughly  made  of  any  sort  of  twigs  and  stems  mixed  with 
hair  and  feathers  and  placed  in  cornices  or  trees.  A 
maple-tree  in  a  small  Missouri  town  contained  at  one  time 
thirty-seven  of  these  nests. 


336  ELEMENTARY  ZOOLOGY 

OTHER    BIRDS. 

Birds  are  readily  and  unmistakably  distinguishable  from 
all  other  kinds  of  animals  by  their  feathers.  They  are 
further  distinguished  from  the  reptiles  on  one  hand  by 
their  possession  of  a  complete  double  circulation  and  by 
their  warm  blood  (normally  of  a  temperature  of  from 
100-112°  F.),  and  from  the  mammals  on  the  other  by 
the  absence  of  milk-glands.  There  are  about  io,OOO 
known  species  of  living  birds ;  they  occur  in  all  countries, 
being  most  numerous  and  varied  in  the  tropics.  Birds 
are  exceptionally  available  animals  for  the  special  atten- 
tion of  beginning  students,  because  of  their  abundance  and 
conspicuousness  and  the  readiness  with  which  their  varied 
and  interesting  habits  may  be  observed.  The  bright 
colors  and  characteristic  manners  which  make  the  identifi- 
cation of  the  different  kinds  easy,  the  songs  and  flight, 
and  the  feeding,  nesting  and  general  domestic  habits  of 
birds  are  all  excellent  subjects  for  personal  field-studies 
by  the  students.  We  shall  therefore  devote  more  atten- 
tion to  the  birds  than  to  the  other  classes  of  vertebrates, 
just  as  we  selected  the  insects  among  the  invertebrates  for 
special  consideration. 

Body  form  and  structure. — The  general  body  form 
and  external  appearance  of  a  bird  are  too  familiar  to  need 
description.  The  covering  of  feathers,  the  modification 
of  the  fore  limbs  into  wings,  and  the  toothless,  beaked 
mouth  are  characteristic  and  distinguishing  external 
features.  The  feathers,  although  covering  the  whole  of 
the  surface  of  the  body,  are  not  uniformly  distributed,  but 
are  grouped  in  tracts  called  pterylce,  separated  by  bare  or 
downy  spaces  called  apteria.  They  are  of  several  kinds, 
the  short  soft  plumules  or  down-feathers,  the  large  stiffer 
contour-feathers,  whose  ends  form  the  outermost  covering 
of  the  body,  the  quill-feathers  of  the  wings  and  tail,  and 


BRANCH  CHORD  AT /I ;   CLASS  AYES:    THE  BIRDS       337 

the  fine  bristles  or  vibrissae  about  the  eyes  and  nostrils 
called  thread-feathers.  The  fore  limbs  are  modified  to 
serve  as  wings,  which  are  well  developed  in  almost  all 
birds.  However,  the  strange  Kiwi  or  Apteryx  of  New 
Zealand  with  hair-like  feathers  is  almost  wingless,  and  the 
penguins  have  the  wings  so  reduced  as  to  be  incapable  of 
flight,  but  serving  as  flippers  to  aid  in  swimming  under- 
neath the  water.  The  ostriches  and  cassowaries  also 
have  only  rudimentary  wings  and  are  not  able  to  fly. 
Legs  are  present  and  functional  in  all  birds,  varying  in 
relative  length,  shape  of  feet,  etc.,  to  suit  the  special 
perching,  running,  wading,  or  swimming  habits  of  the 
various  kinds.  Living  birds  are  toothless,  although 
certain  extinct  forms,  known  through  fossils,  had  large 
teeth  set  in  sockets  on  both  jaws.  The  place  of  teeth  is 
taken,  as  far  as  may  be,  by  the  bill  or  beak  formed  of  the 
two  jaws,  projecting  forward  and  tapering  more  or  less 
abruptly  to  a  point.  In  most  birds  the  jaws  or  mandibles 
are  covered  by  a  horny  sheath.  In  some  water  and  shore 
forms  the  mandibular  covering  is  soft  and  leathery.  The 
range  in  size  of  birds  is  indicated  by  comparing  a  humming- 
bird with  an  ostrich. 

Many  of  the  bones  of  birds  are  hollow  and  contain  air. 
The  air-spaces  in  them  connect  with  air-sacs  in  the  body, 
which  connect  in  turn  with  the  lungs.  Thus  a  bird's 
body  contains  a  large  amount  of  air,  a  condition  helpful 
of  course  in  flight.  The  breast-bone  is  usually  provided 
with  a  marked  ridge  or  keel  for  the  attachment  of  the 
large  and  powerful  muscles  that  move  the  wings,  but  in 
those  birds  like  the  ostriches,  which  do  not  fly  and  have 
only  rudimentary  wings,  this  keel  is  greatly  reduced  or 
wholly  wanting.  The  fore  limbs  or  wings  are  terminated 
by  three  "fingers"  only;  the  legs  have  usually  four, 
although  a  few  birds  have  only  three  toes  and  the  ostriches 
but  two. 


33s  ELEMENTARY  ZOOLOGY 

As  birds  have  no  teeth  with  which  to  masticate  their 
food,  a  special  region  of  the  alimentary  canal,  the  gizzard, 
is  provided  with  strong  muscles  and  a  hard  and  rough 
inner  surface  by  means  of  which  the  food  is  crushed. 
Seed-eating  birds  have  the  gizzard  especially  well  devel- 
oped, and  some  birds  take  small  stones  into  the  gizzard 
to  assist  in  the  grinding.  The  lungs  of  birds  are  more 
complex  than  those  of  batrachians  and  reptiles,  being 
divided  into  small  spaces  by  numerous  membranous  par- 
titions. They  are  not  lobed  as  in  mammals,  and  do  not 
lie  free  in  the  body-cavity,  but  are  fixed  to  the  inner  dorsal 
region  of  the  body.  Connected  with  the  lungs  are  the 
air-sacs  already  referred  to,  which  are  in  turn  connected 
with  the  air-spaces  in  the  hollow  bones.  By  this  arrange- 
ment the  bird  can  fill  with  air  not  only  its  lungs  but  all 
the  special  air-sacs  and  spaces  and  thus  greatly  lower  its 
specific  gravity.  The  vocal  utterances  of  birds  are  pro- 
duced by  the  vocal  cords  of  the  syrinx  or  lower  larynx, 
situated  at  the  lower  end  of  the  trachea  just  where  it 
divides  into  the  two  bronchial  tubes,  the  tracheal  rings 
being  here  modified  so  as  to  produce  a  voice-box  con- 
taining two  vocal  cords  controlled  by  five  or  six  pairs 
of  muscles.  The  air  passing  through  the  voice-box  strikes 
against  the  vocal  cords,  the  tension  of  which  can  be  varied 
by  the  muscles.  In  mammals  the  voice-organ  is  at  the 
upper  or  throat  end  of  the  trachea. 

The  heart  of  birds  is  composed  of  four  distinct  cham- 
bers, the  septum  between  the  two  ventricles,  incomplete 
in  the  Reptilia,  being  in  this  group  complete.  There  is 
thus  no  mixing  of  arterial  and  venous  blood  in  the  heart. 
The  systemic  blood-circulation  being  completely  separated 
from  the  pulmonic,  the  circulation  is  said  to  be  double. 
The  circulation  of  birds  is  active  and  intense ;  they  have 
the  hottest  blood  and  the  quickest  pulse  of  all  animals. 
In  them  the  brain  is  compact  and  large,  and  more  highly 


BRANCH  CHORDATA;  CLASS  AYES:   THE  BIRDS       339 

developed  than  in  batrachians  and  reptiles,  but  the  cere- 
brum has  no  convolutions  as  in  the  mammals.  Of  the 
special  senses  the  organs  of  touch  and  taste  are  apparently 
not  keen;  those  of  smell,  hearing,  and  sight  are  well 
developed.  The  optic  lobes  of  the  brain  are  of  great  size, 
relatively,  compared  with  those  of  other  vertebrate  brains, 
and  there  is  no  doubt  that  the  sight  of  birds  is  keen  and 
effective.  The  power  of  accommodation  or  of  quickly 
changing  the  focus  of  the  eye  is  highly  perfected.  The 
structure  of  the  ear  is  comparatively  simple,  there  being 
ordinarily  no  external  ear,  other  than  a  simple  opening. 
The  organs  of  the  inner  ear,  however,  are  well  developed, 
and  birds  undoubtedly  have  excellent  hearing.  The 
nostrils  open  upon  the  beak,  and  the  nasal  chambers  are 
not  at  all  complex,  the  smelling  surface  being  not  very 
extensive.  It  is  probable  that  the  sense  of  smell  is  not, 
as  a  rule,  especially  keen. 

Development  and  life-history. —  All  birds  are  hatched 
from  eggs,  which  undergo  a  longer  or  shorter  period  of 
incubation  outside  the  body  of  the  mother,  and  which  are, 
in  most  cases,  laid  in  a  nest  and  incubated  by  the  parents. 
The  eggs  are  fertilized  within  the  body  of  the  female,  the 
mating  time  of  most  birds  being  in  the  spring  or  early 
summer.  Some  kinds,  the  English  sparrow,  for  example, 
rear  numerous  broods  each  year,  but  most  species  have 
only  one  or  at  most  two.  The  eggs  vary  greatly  in  size 
and  color-markings,  and  in  number  from  one,  as  with 
many  of  the  Arctic  ocean  birds,  to  six  or  ten,  as  with  most 
of  the  familiar  song-birds,  or  from  ten  to  twenty,  as  with 
some  of  the  pheasants  and  grouse.  The  duration  of  in- 
cubation (outside  the  body)  varies  from  ten  to  thirty  days 
among  the  more  familiar  birds,  to  nearly  fifty  among  the 
ostriches. '  The  temperature  necessary  for  incubation  is 
about  40°  C.  (i 00°  F.).  Among  polygamous  birds 
(species  in  which  a  male  mates  with  several  or  many 


340  ELEMENTARY  ZOOLOGY 

females)  the  males  take  no  part  in  the  incubation  and  little 
or  none  in  the  care  of  the  hatched  young ;  among  most 
monogamous  birds,  however,  the  male  helps  to  build  the 
nest,  takes  his  turn  at  sitting  on  the  eggs,  and  is  active  in 
bringing  food  for  the  young,  and  in  defending  them  from 
enemies.  The  young,  when  ready  to  hatch,  break  the 
egg-shell  with  the  "  egg-tooth,"  a  horny  pointed  projec- 
tion on  the  upper  mandible,  and  emerge  either  blind  and 


FIG.  134. — The  nest  and  eggs  of  the  black  phcebe,  Sayornis  nigricans. 
(Photograph  by  J.  O.  Snyder.) 

almost  naked,  dependent  upon  the  parents  for  food  until 
able  to  fly  (altricial  young),  or  with  eyes  open  and  with 
body  covered  with  down,  and  able  in  a  few  hours  to  feed 
themselves  (precocial  young). 

More  details  regarding  the  eggs,  nest,  and  young  of 
birds  will  be  given  later  in  this  chapter. 

Classification. — The  class  Aves  is  usually  divided  into 
numerous  orders,  the  number  and  limits  of  these  as  pub- 
lished in  zoological  manuals  varying  according  to  the 


BRANCH  CHORD  AT  A;   CLASS  AVES :   THE  BIRDS       341 

opinions  of  various  zoologists.  The  rank  of  an  order  in 
this  group  is  far  lower  than  in  most  other  classes.  In 
other  words,  the  orders  are  very  much  alike  and  are 
recognized  mainly  for  the  convenience  in  breaking  up  the 
vast  assemblage  of  species.  In  North  America  practically 
all  the  ornithologists  have  agreed  upon  a  scheme  of 
classification,  which  will  therefore  be  adopted  in  this  book. 
According  to  this  classification  the  eight  hundred  (approxi- 
mately) known  species  of  North  American  birds  represent 
seventeen  orders.  Certain  recognized  orders,  for  example, 
the  ostriches,  are  not  represented  naturally  in  North 
America  at  all.  As  birds  can  usually  be  readily  identi- 
fied, the  species  being  easily  distinguished  by  general 
external  appearance,  and  as  there  are  many  excellent 
book-guides  to  their  classification,  the  beginning  student 
can  specially  well  begin  with  them  his  study  of  systematic 
zoology,  which  concerns  the  identification  and  classifica- 
tion of  species.  In  a  later  paragraph  are  given  therefore 
some  suggestions  for  field  and  laboratory  work  in  the 
determination  of  local  bird-faunae.  In  the  following  para- 
graphs each  of  the  American  orders  is  briefly  discucc=ed,  as 
is  also  the  foreign  order  of  ostriches. 

The  ostriches,  cassowaries,  etc.  (Ratitae). — The  os- 
triches, familiar  to  all  from  pictures  and  to  some  from 
live  individuals  in  zoological  gardens  and  menageries, 
or  stuffed  specimens  in  museums,  together  with  a  few 
other  similar  large  species,  are  distinguished  from  all 
other  birds  by  having  the  breast-bone  flat  instead  of 
keeled.  There  are  about  a  score  of  species  of  ostriches 
and  ostrich-like  birds  all  confined  to  the  southern  hemi- 
sphere. In  them  the  wings  are  so  reduced  that  flight  is 
impossible,  but  the  legs  are  long  and  strong,  and  they  can 
run  as  swiftly  as  a  galloping  horse.  They  are  said  to  have 
a  stride  of  over  twenty  feet.  They  use  their  legs  also  as 
weapons,  kicking  viciously  when  angered.  The  true 


342 


ELEMENTARY  ZOOLOGY 


ostriches  (Struthio  camelus)  (fig.  135)  live  in  Africa.  They 
are  the  largest  living  birds,  reaching  a  height  of  nearly 
seven  feet  and  weighing  as  much  as  two  hundred  pounds. 
They  are  hunted  for  their  feathers,  and  are  now  kept  in 
captivity  and  bred  in  South  Africa  and  California  for 
the  same  purpose.  About  five  million  dollars'  worth  of 


FlG.  135. — Ostriches  on  ostrich  farm  at  Pasadena,  California.      (Photo- 
graph from  life.) 

ostrich-feathers  are  used  each  year.  The  eggs,  which  are 
from  five  to  six  inches  long  and  nearly  five  inches  thick, 
are  laid  in  shallow  hollows  scooped  out  in  the  sand  of  the 
desert.  The  male  undertakes  most  of  the  incubation, 
although  when  the  sun  is  hot  no  brooding  is  necessary. 


BRANCH  CHORD  AT  A;  CLASS  AYES:   THE  BIRDS       343 

The  young  (fig.  136)  hatch  in  from  seven  to  eight  weeks, 
and  can  run  about  immediately. 

The  rheas,  found  in  South  America,  and  the  cassowaries 
of  Australia  are  the  only  other  living  ostrich-like  birds. 


Fir..  136. — Young  ostriches  just  from  egg:  on  ostrich  farm  at  Pasadena, 
California.     (Photograph  from  life.) 

Their  feathers  are  of  much  less  value  than  those  of  the 
true  ostrich. 

The  loons,  grebes,  auks,  etc.  (Pygopodes). — The 
loons,  grebes,  and  auks  are  aquatic  birds,  living  in  both 
ocean  and  fresh  waters.  Their  feet  are  webbed  or  lobed, 
and  their  legs  set  so  far  back  that  walking  is  very  difficult 
and  awkward.  But  all  the  birds  of  this  order  are  excel- 
lent swimmers  and  divers.  They  are  distinctively  the 
diving  birds.  They  have  short  wings  and  almost  no  tail. 
The  dab-chick  or  pied-billed  grebe  (Podilymbus  podiccps) 
is  common  in  ponds  over  all  the  country.  Its  eggs  are 
laid  in  a  floating  nest  of  pond  vegetation  and  are  often 
covered  with  decaying  plants.  The  horned  grebe 
(Colymbus  auritns)  is  common  west  of  the  Mississippi  in 
lakes  and  ponds.  The  loon  or  great  northern  diver 


344 


ELEMENTARY  ZOOLOGY 


BRANCH  CHORD  AT  A;   CLASS  AYES:    THE  BIRDS      345 

(Gavin  nnbcr),  found  all  over  the  United  States  in  winter, 
is  the  largest  of  this  group,  reaching  a  length  (from  bill  to 
tip  of  tail)  of  three  feet.  It  is  black  above  with  many 
small  white  spots,  and  with  a  patch  of  white  streaks  on 
each  side  of  the  neck  and  on  the  throat;  it  is  white  on 
breast  and  belly.  The  female  is  duller,  being  brownish 
instead  of  black. 

The  auks,  guillemots,  puffins,  and  murres  (fig.  137) 
are  ocean  birds  which  gather,  in  the  breeding  season,  in 
countless  numbers  on  the  bleak  rocks  and  inaccessible 
cliffs  of  the  northern  oceans.  Each  female  lays  a  single 
egg  (in  some  cases  two  or  at  most  three)  on  the  bare  rock 
or  in  a  crevice  or  sort  of  burrow.  These  birds  mostly  fly 
well,  but  are  especially  at  home  in  the  water,  feeding  ex- 
clusively on  animal  substances  found  there.  A  famous 
species  is  the  great  auk  (A  lea  impcnnis],  which  has 
become  extinct  in  historical  times.  The  last  living  speci- 
men was  seen  in  1844. 

The  gulls,  terns,  petrels,  and  albatrosses  (Longi- 
pennesi. — The  Longipennes  are  water-birds,  mostly 
maritime,  with  webbed  feet  and  very  long  and  pointed 
wings.  They  are  all  strong  flyers,  and  most  of  them 
are  beautiful  birds.  Their  prevailing  colors  are  white, 
slaty  or  lead-blue,  black,  and,  in  the  young,  mottled 
brownish.  They  subsist  chiefly  on  fish,  but  any  animal 
substance  \vill  be  eagerly  picked  up  from  the  water ;  some 
of  the  gulls  forage  inland.  Occasionally  great  flocks  may 
be  seen  following  a  plow  near  the  shore  and  feeding  on 
the  grubs  and  worms  exposed  in  the  freshly-turned  soil. 
Some  of  the  gulls,  like  the  great  black-backed  gull  (Lams 
marinus},  attain  a  length  of  two  and  one-half  feet.  The 
terns  (Sterna)  are  mostly  smaller  than  the  gulls,  have  a 
bill  not  so  heavy  and  not  hooked,  and  have  the  tail 
forked. 

The  fulmars,  shearwaters,  petrels,  and  albatrosses  are 


346  ELEMENTARY  ZOOLOGY 

strictly  maritime.  The  albatrosses  are  very  large,  the 
largest  being  three  feet  long  with  a  spread  of  wing  of 
seven  feet.  They  are  often  found  flying  easily  over  the 
open  ocean  at  great  distances  from  land.  Like  the  auks 
and  puffins,  the  fulmars  and  shearwaters  gather  in  extra- 
ordinary numbers  on  rocky  ocean  islets  or  cliffs  of  the 
coast  to  breed. 

The  cormorants,  pelicans,  etc.  (Steganopodes). — The 
Steganopodes  are  water-birds  with  full-webbed  feet,-  and 
prominent  gular  pouch,  swimmers  rather  than  flyers  like 
the  Longipennes.  The  cormorants  (Phalacrocorax)  in- 
habit rocky  coasts  and  are  green-eyed,  large,  heavy, 
black  birds  with  greenish-purple  and  violet  iridescence ; 
they  are  among  the  most  familiar  of  seashore  birds.  They 
feed  chiefly  on  fish  and  dive  and  swim  under  water  with 
great  ability.  Cormorants  are  rather  gregarious,  keeping 
together  in  small  groups  when  fishing,  migrating  often  in 
great  flocks,  and  in  the  breeding  season  gathering  in 
immense  numbers  on  certain  rocky  cliffs  or  islets.  They 
build  their  nests  of  sticks  and  sea-weed ;  the  eggs  are 
three  or  four,  and  usually  bluish  green  with  white,  chalky 
covering  substance. 

The  pelicans  are  large,  long-winged,  short-legged 
water-birds  with  enormous  bill  and  large  gular  sac  which 
is  used  as  a  dip-net  to  catch  fish.  There  are  three  species 
in  North  America,  the  white  pelican  (Pelccaniis  crytJiro- 
rJiyncJnts]  occurring  over  most  of  the  United  States,  the 
brown  pelican  (P.  fiiscus]  of  the  Gulf  of  Mexico,  and 
the  California  brown  pelican  (P.  calif  or nicus}  of  the  Pacific 
coast. 

An  interesting  member  of  this  order  is  the  famous 
frigate  or  man-of-war  bird  (Frcgata  aquila),  with  very  long 
wings*  and  tail  and  feet  extraordinarily  small.  The 
frigates  have  the  greatest  command  of  wing  of  all  the 
birds.  They  cannot  dive  and  can  scarcely  swim  or  walk. 


BRANCH  CHORDATA;   CLASS  AYES:    THE  BIRDS       347 

The  ducks,  geese,  and  swans  (Anseres).— The  familiar 
wild  ducks,  of  which  there  are  forty  species  in  North 
American  fresh  and  salt  waters ;  the  geese,  of  which  there 
are  sixteen  species,  and  the  three  species  of  wild  swans 
constitute  the  order  Anseres.  The  bill  in  these  birds  is 
more  or  less  flattened  and  is  also  lamellate,  i.e.  furnished 
along  each  cutting-edge  with  a  regular  series  of  tooth-like 
processes;  the  feet  are  webbed,  and  the  body  is  heavy 
and  flattened  beneath.  Of  the  fresh- water  or  inland 
ducks,  the  more  familiar  are  the  mallard  (Anas  bosc/ias\ 
a  large  duck  with  head  (male)  and  upper  neck  rich  glossy 
green;  the  blue-winged  teal  (Qucrqiiedula  discors)  and 
green-winged  teal  (Nettion  carolinense] ;  the  shoveller 
(Spatula  clypeata)  with  spoon-shaped  bill;  the  beautiful 
crested  wood-duck  (Aix  sponsa}\  the  expert  diver,  the 
plump  little  ruddy  duck  (Erismatura  rubida}^  and  others. 
Of  the  coastwise  ducks,  the  canvas-back  (Aythya  val- 
lisncria)  is  famous  because  of  its  fine  flavor,  while  among 
the  strictly  maritime  ducks  the  eiders  (Somatcria},  which 
live  in  Arctic  regions,  are  well  known  for  their  fine  down. 
Of  the  geese,  the  commonest  is  the  well-known  Canada 
goose  (Brant a  canadcnsis],  while  the  pure- white  snow- 
goose  (CJien  hyperbored],  with  black  wing-feathers  and 
red  bill,  is  not  unfamiliar.  The  wild  swans  (Olor]  are  the 
largest  birds  of  the  order,  and  are  less  familiar  than  the 
ducks  and  geese. 

The  ibises,  herons,  and  bitterns  (Herodiones). — The 
tall,  long-necked,  long-legged,  wading  birds,  known  as 
herons  and  ibises,  compose  a  small  order,  the  Herodiones, 
of  which  but  few  representatives  are  at  all  familiar. 
Perhaps  the  most  abundant  species  is  the  green  heron 
(Ardea  virescens)  or  "  fly-up-the-creek, "  one  of  the 
smaller  members  of  the  order.  The  crown,  back,  and 
wings  are  green,  the  neck  purplish  cinnamon,  and  the 
throat  and  fore  neck  white-striped.  This  bird  is  com- 


348  ELEMENTARY  ZOOLOGY 

monly  seen  perching  on  an  overhanging  limb,  or  flying 
slowly  up  or  down  some  small  stream.  The  great  blue 
heron  (Ardea  herodias)  is  common  over  the  whole 
country.  It  is  four  feet  long  and  grayish  blue,  marked 
with  black  and  white.  It  may  be  seen  standing  alone  in 
wet  meadows  or  pastures,  or  flying  heavily,  with  head 
drawn  back  and  long  legs  outstretched.  It  breeds 
singly,  but  oftener  in  great  heronries,  in  trees  or  bushes. 
Its  large  bulky  nests  contain  three  to  six  dull,  greenish- 
blue  eggs  about  two  and  one-half  inches  long.  The  white 
egrets  of  the  Southern  States  are  shot  for  their  plumes  and 
have  been  locally  exterminated  in  some  places.  The 
night-herons  (Nycticorax)  differ  from  the  other  forms  in 
having  both  the  neck  and  legs  short.  The  bittern 
(Botatirus  lentiginosus),  Indian  hen,  stake-driver,  or 
thunder-pumper,  as  it  is  variously  called,  is  a  familiar 
member  of  the  order,  found  in  marshes  and  wet  pastures, 
and  known  by  its  extraordinary  call,  sounding  like  the 
* '  strokes  of  a  mallet  on  a  stake. ' '  In  color  it  is  brownish, 
freckled  and  streaked  with  tawny  whitish  and  blackish. 
Its  nest  is  made  on  the  ground;  its  eggs,  from  three  to 
five  in  number,  are  brownish  drab  and  about  two  inches 
long. 

The  cranes,  rails,  and  coots  (Paludicolae).  —The  cranes, 
of  which  three  species  are  known  in  North  America,  are 
large  birds  with  long  legs  and  neck,  part  of  the  head  being 
naked  or  with  hair-like  feathers.  The  rare  whooping 
crane  (Grus  americana)  is  pure  white  with  black  on  the 
wings,  and  is  fifty  inches  long  from  tip  of  bill  to  tip  of 
tail.  The  sand-hill  crane  (G.  mexicana)  is  slaty  gray  or 
brownish  in  color,  never  white,  and  although  rare  in  the 
East  is  quite  common  in  the  South  and  West.  Cranes 
build  nests  on  the  ground,  and  lay  but  two  eggs,  about 
four  inches  long,  brownish  drab  in  color  with  large  irreg- 
ular spots  of  dull  chocolate-brown. 


BRANCH  CHORD  AT  A;   CLASS  AYES:    THE  BIRDS       349 

The  rails  are  smaller  than  the  cranes,  with  short  wings 
and  very  short  tail.  They  live  in  marshes  and  swamps, 
and  in  flying  let  the  legs  hang  down.  Their  legs  are 
strong,  and  for  escape  they  trust  more  to  speed  in  running 
than  to  flight.  They  are  hunted  for  food.  The  most 
abundant  rail  is  the  "Carolina  crake"  or  "sora" 
(Porsana  Carolina),  small  and  olive-brown  with  numerous 
sharp  white  streaks  and  specks.  Many  of  these  birds  are 
shot  each  year  during  migration  in  the  reedy  swamps  of 
the  Atlantic  States.  The  American  coot  or  mud-hen 
(Fulica  americana),  dark  slate-color  with  white  bill,  is  one 
of  the  most  familiar  pond-birds  over  all  temperate  North 
America.  Its  nest  consists  of  a  mass  of  broken  reeds 
resting  on  the  water;  the  eggs  number  about  a  dozen, 
and  are  clay-color  with  pin-head  dots  of  dark  brown. 

The  snipes,  sandpipers,  plover,  etc.  (Limicolae). — The 
large  order  Limicolae,  the  shore-birds,  includes  the 
slender-legged,  slender-billed,  round-headed,  rather 
small  wading  birds  of  shores  and  marshes  familiar  to 
us  as  snipes,  plovers,  sandpipers,  curlews,  yellow-legs, 
sandpeeps,  turnstones,  etc.  Most  of  them  are  game- 
birds,  such  forms  as  the  woodcock  and  Wilson's  or 
English  snipe  being  much  hunted.  The  food  of  these 
birds  consists  of  worms  and  other  small  animals,  which 
are  chiefly  obtained  by  probing  with  the  rather  flexible, 
sensitive,  and  usually  long  bill  in  the  mud  or  sand.  The 
killdeer  (ALgialitis  vocifera),  familiar  to  all  in  its  range 
by  its  peculiar  call  and  handsome  markings,  the  upland 
or  field  plover  (Bartramia  longicauda),  with  its  long  legs 
and  melodious  quavering  whistle,  the  tall,  yellow-shanked 
"telltale  "  or  yellow-legs  (Tetanus  mclanoleucns)  of  the 
marshes  and  wet  pastures,  are  among  the  most  wide- 
spread and  familiar  species  of  the  order.  On  the  seashore 
*  the  dense  flocks  of  white-winged,  whisking  sandpipers 
and  the  quickly  running  groups  of  plump  ring-necked 


35°  ELEMENTARY  ZOOLOGY 

plover  are  familiar  sights.  One  of  the  largest  birds  of 
this  order  is  the  long-billed  curlew  (Numenius  longirostris) 
of  the  upland  pastures.  The  bill  of  the  curlew  is  long 
and  curved  downwards.  The  nests  of  these  shore-birds 
are  made  on  the  ground  and  are  usually  little  more  than 
shallow  depressions  in  which  the  few  spotted  eggs  (four 
is  a  common  number)  are  laid.  The  young  are  precocial. 
The  grouse,  quail,  pheasants,  turkeys,  etc.  (Gallinse). 
— The  Gallinae  include  most  of  the  domestic  fowls,  as  the 
hen,  turkey,  peacock,  guinea-fowls,  and  pheasants,  and 
the  grouse,  quail,  partridges,  and  wild  turkeys.  The 
chief  game-birds  of  most  countries  belong  to  this  order. 
They  have  the  bill  short,  heavy,  convex,  and  bony, 
adapted  for  picking  up  and  crushing  seeds  and  grains 
which  compose  their  principal  food.  Their  legs  are  strong 
and  usually  not  long,  and  are  often  feathered  very  low 
down.  The  Gallinae  are  mostly  terrestrial  in  habit  and 
are  sometimes  known  as  the  Rasores  or  "  scratchers. " 
Among  the  more  familiar  wild  gallinaceous  birds  are  the 
quail  or  "  Bob  white  "  (Colinus  virginianus),  abundant  in 
eastern  and  central  United  States,  the  ruffed  grouse 
(Bonasa  umbellus]  of  the  Eastern  woods,  and  the  prairie- 
chicken  (Tympanuchus  americanus)  of  the  Western  prairies. 
The  sage-hen  (Centrocercus  urophasianus),  the  largest  of 
the  American  grouse,  reaching  a  length  of  two  and  one- 
half  feet,  is  an  interesting  inhabitant  of  the  sterile  sage- 
brush plains  of  the  West.  The  ptarmigan  (Lagopus)  or 
snow-grouse,  represented  by  several  species,  are  found 
either  among  the  rocks  and  snow-banks  above  timber 
line  on  high  mountains,  or  in  the  Arctic  regions.  In 
summer  their  plumage  is  brown  and  white ;  in  winter  they 
turn  pure  white  to  harmonize  with  the  uniform  snow- 
covering.  On  the  Pacific  coast  are  several  species  of 
quail,  all  differing  much  from  those  of  the  East.  These 
Western  species  have  beautiful  crests  of  a  few  or  several 


BRANCH  CHORD  AT  A;  CLASS  AYES:   THE  BIRDS       35 l 

long  plume-feathers,  the  body-plumage  being  also  un- 
usually beautiful.  The  eggs  of  all  the  Gallinae  are  numer- 
ous and  are  laid  in  a  rude  nest  or  simply  in  a  depression 
on  the  ground.  In  many  of  the  species  polygamy  is  the 
rule.  The  young  are  precocial. 

The  doves  and  pigeons  (Columbae). — The  doves  and 
pigeons  constitute  a  small  order,  the  Columbae,  closely 
related  to  the  Gallinae.  A  distinguishing  characteristic 
of  the  Columbae  lies  in  the  bill,  which  is  covered  at  the 
base  with  a  soft  swollen  membrane  or  cere  in  which  the 
nostrils  open.  The  members  of  this  order  feed  on  fruits, 
seeds,  and  grains.  Our  most  familiar  wild  species  is  the 
mourning-dove  or  turtle-dove  (Zenaidura  macroura)  found 
abundantly  all  over  the  country.  It  lays  two  eggs  in  a 
loose  slight  nest  in  a  low  tree  or  on  the  ground.  The 
beautiful  wild  or  passenger  pigeon  (Ectopistes  migratorius) 
was  once  extremely  abundant  in  this  country,  moving 
about  in  tremendous  flocks  in  the  Eastern  and  Central 
States.  But  it  has  been  so  relentlessly  hunted  that  the 
species  is  apparently  becoming  extinct.  In  the  Rocky 
and  Sierra  Nevada  mountains  is  a  rather  large  dove,  the 
band-tailed  pigeon  (Columba  fasciatd],  which  subsists 
chiefly  on  acorns.  The  domestic  pigeon  represented  by 
numerous  varieties,  pouters,  carriers,  ruff-necks,  fan-tails, 
etc.,  is  the  artificially  selected  descendant  of  the  rock-dove 
(Columba  livid).  The  young  of  all  pigeons  are  altricial. 

The  eagles,  owls,  and  vultures  (Raptores).— The 
"birds  of  prey  "  compose  one  of  the  larger  orders,  the 
members  of  which  are  readily  recognizable.  In  all  the 
bill  is  heavy,  powerful,  and  strongly  hooked  at  the  tip. 
The  feet  are  strong,  with  long,  curved  claws  (small  in  the 
vultures)  and  are  fitted  for  seizing  and  holding  living 
prey,  such  as  smaller  birds,  fish,  reptiles,  and  mammals 
which  constitute  the  principal  food  of  the  true  raptorial 
species.  The  vultures  feed  on  carn'on.  The  turkey 


352 


ELEMENTARY  ZOOLOGY 


buzzard  (Cat  hart  es  aura)  is  the  most  familiar  of  the  three 
species  of  carrion-feeding  Raptores  found  in  the  United 
States.  The  buzzard  nests  on  the  ground  or  in  hollow 
stumps  or  logs,  and  lays  two  white  eggs  (sometimes  only 
one)  blotched  with  brown  and  purplish.  The  largest 
North  American  vulture  is  the  California  condor  (Pseudo- 
grypJius  calif  or  niarius),  which  attains  a  length  of  four  and 
one-half  feet,  with  a  spread  of  wing  of  nine  and  one-half 


FIG.  138. — Screech-owl,  Megascops  asio.     (Photograph  by  A.  L.  Princeton 
permission  of  Macmillan  Co.) 

feet.  Of  the  eagles,  the  most  widespread  and  commonest 
is  the  bald  eagle  (Ha  licet  us  leucocephahts).  It  is  three 
feet  long  and  when  adult  has  the  head  and  neck  white. 
The  golden  eagle  (Aquila  cJiryscetos]  has  the  neck  and 
head  tawny  brown.  Of  the  many  species  of  hawks,  the 
marsh  harrier  (Circus  Jiudsonius),  abundant  all  over  the 
country  and  readily  known  by  its  white  rump,  is  one  of 


BRANCH   CHORD  AT  A:   CLASS  AYES:    THE  BIRDS       353 

the  most  familiar.  The  name  "chicken-hawk  "  is  given 
to  two  or  three  different  species  of  large  broad-winged 
hawks  of  the  genus  Buteo.  -The  stout  little  sparrow-hawk 
{Falco  sparverius],  common  over  the  whole  country,  is 
familiar  and  readily  recognizable  by  its  pronounced  bluish 
and  black  wings  and  black-and-white  banded  chestnut 
tail.  Altogether  fifty  species  of  hawks  and  eagles  are 
found  in  this  country.  Of  the  owls,  the  barn-owl  (Strix 
pratincold)  with  its  long  triangular  face  and  handsome 
mottled  and  spotted  tawny  coat  is  more  or  less  familiar, 
the  great  horned  owl  (Bubo  virginianus),  the  snowy  owl 
(Nyctea  nycteci),  and  the  great  gray  owl  (Scotiaptex 
cinerea)  are  the  common  large  species,  while  the  red 
screech-o\vl  (Megaseops  asio)  (fig.  138),  the  most  abundant 
owl  in  the  country,  and  the  strange  burrowing  owl 
{Speotyto  cnniciilaria],  which  lives  in  the  holes  of  prairie- 
dogs  and  ground-squirrels  in  the  West,  are  familiar  smaller 
ones.  Thirty-two  species  of  owls  are  recorded  from 
North  America. 

The  parrots  (Psittaci). — The  parrots,  of  which  only 
one  species  is  native  in  the  United  States,  constitute  an 
interesting  order  of  birds,  the  Psittaci.  They  are  abun- 
dant in  tropical  America.  They  have  a  very  thick 
strongly  hooked  bill,  with  a  thick  and  fleshy  tongue. 
The  feet  have  two  toes  pointing  forward  and  two  back- 
ward. The  plumage  is  usually  brightly  and  gaudily 
colored.  The  natural  voice  is  harsh  and  discordant,  but 
many  of  the  species  can  imitate  writh  surprising  cleverness 
the  speech  of  man.  Parrots  are  long-lived  and  usually 
docile,  and  are  much  kept  as  pets.  The  single  native 
species,  the  Carolina  paroquet  (Conurus  carolinensis),  is 
about  a  foot  in  length,  is  green,  with  yellow  head  and 
neck  and  orange-red  face.  Its  range  once  extended  from 
the  Gulf  of  Mexico  north  to  the  Great  Lakes,  but  it  has 
been  nearly  exterminated  in  all  the  States  but  Florida. 


354  .    ELEMENTARY  ZOOLOGY 

The    cuckoos    and     kingfishers      (Coccyges). — The 

cuckoos  and  kingfishers  are  regarded  as  constituting  an 
order,  Coccyges,  a  small  group  whose  members  are  with- 
out any  definite  bond  of  union.  Only  ten  species  of  North 
American  birds  belong  to  this  order.  The  yellow-billed 
and  black-billed  cuckoos  (Coccyzus]  or  "  rain-crows  "  are 
long-tailed,  slender,  lustrous  drab  birds,  which  lay  their 
eggs  in  the  nests  of  others.  They  are  notable  for  their 
peculiar  rolling  call.  On  the  plains  and  hills  of  California 
and  the  southwest  lives  the  road-runner  or  chaparral  cock 
(Geococcyx  calif  or  ma  mis],  a  strange  bird  belonging  to  the 
cuckoo  family.  It  is  nearly  two  feet  long,  of  which  length 
the  tail  makes  half.  These  birds  run  so  rapidly  that  a 
horse  is  little  more  than  able  to  keep  up  with  them.  They 
feed  on  fruits,  various  reptiles,  insects,  etc.  The  one 
common  kingfisher  of  this  country,  the  belted  kingfisher 
(Ceryle  alcyon),  a  thick-set,  heavy-billed,  ashy  blue-and- 
white  bird,  is  familiar  along  streams.  As  it  flies  swiftly 
along  it  gives  its  rattling  cry.  It  nests  in  deep  holes  in 
the  stream-banks,  and  lays  six  or  eight  crystal-white 
spheroidal  eggs. 

The  woodpeckers  (Pici). — The  familiar  woodpeckers 
and  sap-suckers  compose  a  well-defined  order,  Pici,  which 
is  represented  in  North  America  by  twenty-five  species. 
The  bill  of  the  woodpecker  is  stout  and  strong,  usually 
straight,  fitted  for  driving  or  boring  into  wood  ;  the  tongue 
is  long,  sharp-pointed,  and  barbed,  fitted  for  spearing 
insects.  The  feet  have  two  toes  turned  forward  and  two 
backward;  the  tail-feathers  are  stiff  and  sharp-pointed 
and  help  support  the  bird  as  it  clings  to  the  vertical  side 
of  a  tree-trunk  or  branch  (fig.  139).  The  food  of  most 
woodpeckers  consists  chiefly  of  insects,  usually  wood- 
boring  larvae  (grubs).  These  birds  do  much  good  by 
destroying  many  noxious  insect  pests  of  trees.  A  few 
species,  the  true  sap-suckers,  probably  feed  on  the  sap  of 


BRANCH   CHORD  AT  A;   CLASS  AYES:    THE  BIRDS       355 


trees.  Their  nests  are  made  in  holes  in  trees,  and  the 
eggs  are  pure  white  and  rounded.  The  harsh  and  shrill 
cries  of  the  woodpeckers  are  familiar  to  all. 

The  largest  and  one  of  the  most  interesting  wood- 
peckers is  the  ivory-billed  (Campephilus  principalis], 
twenty  inches  long,  glossy  blue-black,  with  a  high  head- 


1 


W.  E. 


FlG.  139.  —  The  yellow-hammer,  Colaptes  auratus.     (Photograph  by 
Carlin;  permission  of  G.  O.  Shields.) 

crest  which  is  scarlet  in  the  male.  This  bird  lives  in  the 
heavily  wooded  swamps  of  the  Southern  States.  Among 
the  more  abundant  and  widespread,  and  hence  better 
known,  woodpeckers  are  the  yellow-hammers  (fig.  139) 


356  ELEMENTARY  ZOOLOGY 

or  flickers  (Colaptes  auratus  in  the  East,  C.  cafcr  in  the 
West),  the  red-headed  woodpecker  {Melaucrpcs  erytJiro- 
cephalns],  with  its  crimson  head  and  neck  and  pure-white 
<4yest";  and  the  black-and-white  downy  {Dry abates 
pubcscens]  and  hairy  (/?.  villosus]  woodpeckers  or  ^sap- 
suckers."  The  California  woodpecker  (M.  fonnicivorus), 
a  near  relative  of  the  red-headed  woodpecker,  has  the 
curious  habit  of  boring  small  holes  in  the  bark  of  oak-  or 
pine-trees  and  sticking  acorns  into  these  holes.  Some- 
times thousands  of  acorns  are  put  into  the  bark  of  one 
tree,  to  which  the  birds  come  occasionally  to  break  open 
some  acorns  and  feed  on  the  grubs  inside. 

The  whippoorwills,  chimney-swifts  and  humming- 
birds (Macrochires). — All  the  birds  of  this  order  are 
remarkable  for  their  power  of  flight.  They  have  long  and 
pointed  wings;  their  feet  are  small  and  weak  and  used 
only  for  perching  or  clinging.  All  feed  on  insects,  which 
are  caught  on  the  wing  by  the  short-beaked,  wide- 
mouthed  swifts  and  whippoorwills  and  extracted  from 
flower-cups  by  the  humming-birds  with  their  long  and 
slender  bills.  The  whippoorwill  (AntrosttfmHs  vociferns} 
is  common  in  the  woods  of  the  East  and  is  readily  known 
by  its  call.  Its  two  brown-blotched  white  eggs  are  laid 
loose  on  the  ground  or  on  a  log  or  stump.  The  night- 
hawrk  {Chordeiles  virginianns],  common  over  the  whole 
country,  is  seen  at  twilight  flying  vigorously  about  in 
its  search  for  insects.  Its  nesting  habits  are  like  those 
of  the  whippoorwill.  The  sooty-brown  chimney-swifts 
(CJicetura  pelagica],  popularly  confused  with  the  swallows, 
are  the  common  inhabitants  of  old  chimneys,  in  which  they 
build  their  curious  saucer-shaped  open-work  nests.  Their 
eggs  are  pure  white  and  number  four  or  five.  Of  the 
humming-birds  but  one  species,  the  ruby-throat  ( Trochihis 
colubris],  is  to  be  found  in  the  Eastern  States,  but  in  the 
western  and  especially  southwestern  parts  of  the  country 


BRANCH   CHORD  AT  A ;   CLASS  Al/ES :    THE   BIRDS       357 


several  other  species  occur.  In  all  seventeen  species 
have  been  found  in  the 
United  States.  The  nests 
(fig.  140)  of  the  hummers 
are  very  dainty  little  cups 
lined  with  hair  or  wool  or 
plant -down.  The  ruby- 
throat  lays  two  tiny  pure- 
white  eggs. 

The  perchers  (Passeres). 
—Nearly  one-half  of  the 
birds  of  North  America  be- 
long to  the  great  order  Pas- 
seres,  and  of  all  the  known 
birds  of  the  world  more  than 
half  are  included  in  it.  The 
Passeres  or  perching  birds 
include  the  familiar  songf- 

O 

birds  and  a  great  majority 
of  the  birds  of  the  garden, 
the  forest,  the  roadside,  and 
the  field.  The  feet  of  these 
birds  always  have  four  toes 
and  are  fitted  for  perching. 
The  syrinx  or  musical  ap- 
paratus is,  in  most,  well 
developed.  The  nesting 
and  other  domestic  habits 
are  various,  but  the  young 
are  always  hatched  in  a 
helpless  condition  and  have  FIG.  140.— Nest  and  eggs  of  ruby- 
to  be  fed  and  otherwise  throat.  humming  bird,  Trochiius 

colubrts,  seen  from  above,   in  apple- 
Cared  for  by  the  parents  for        tree.     (Photograph  by  E.  G.  Tabor; 

a   longer   or   shorter  time.       Permission trflfocmillan  Co.) 
The  North  American  species  of  this  order  are  grouped  into 


358 


ELEMENTARY  ZOOLOGY 


eighteen  families,  as  the  fly-catcher  family  (Tyrannidae), 
the  crow  family  (Corvidae),  the  sparrows  and  finches 
(Fringillidae),  the  swallows  (Hirundintdae),  the  warblers 
(Mniotiltidse),  the  wrens  (Troglodytidae),  the  thrushes, 
robins  and  bluebirds  (Turdidae),  etc.  In  this  book 
nothing  can  be  said  of  the  various  species  which  belong 
to  this  order.  However,  as  the  passerine  birds  are 


FlG.  141. — Horned  larks.  Otocoris  alpestris,  and  snowttakes,  Plcclrophcnax 
nivalis.  (Photograph  from  life  by  H.  W.  Menke;  permission  of  Mac- 
millan  Co.) 

those  which  most  immediately  surround  us  and  which,  by 
their  familiar  songs  and  nesting  habits,  most  interest  us, 
the  out-door  study  of  birds  by  beginning  students  will  be 
devoted  chiefly  to  the  members  of  this  order,  and  many 
species  will  soon  be  got  acquainted  with.  The  robin  and 
bluebird  will  introduce  us  to  the  shyer  and  less  familiar 
song-thrushes;  the  study  of  the  kingbird  or  bee-martin 


BRANCH  CHORD  AT  A;   CLASS  AYES:    THE  BIRDS       359 

will  interest  us  in  some  of  the  other  fly-catchers;  from  the 
familiar  chipping  sparrow  and  tree-sparrow  we  shall  be 
led  to  look  for  their  cousins  the  swamp-sparrows  and 
song-sparrows,  and  the  larger  grosbeaks  and  cross-bills, 
and  so  on  through  the  order. 

Determining  and  studying  the  birds  of  a  locality. — 
To  identify  the  various  species  of  birds  in  the  locality  of 
the  school  it  uill  be  necessary  to  have  some  book  giving 
the  descriptions  of  all  or  most  of  the  species  of  the  region, 
with  tables  and  keys  for  tracing  out  the  different  forms. 
Such  manuals  or  keys  are  numerous  now ;  the  study  of 
birds  is  one  of  the  most  popular  lines  of  nature  study,  and 
a  host  of  bird  books  has  been  published  in  the  last  few 
years.  The  best  general  manual  is  Coues's  "  Key  to  the 
Birds  of  North  America,"  which  includes  not  only  keys 
for  tracing  and  descriptions  of  all  the  known  species  of 
birds  on  this  continent,  but  also  accounts  of  the  distribu- 
tion, of  the  nesting  and  eggs,  and  of  the  plumage  of  the 
young  birds,  besides  a  thorough  introduction  to  the 
anatomy  and  physiology  of  birds,  and  directions  for  col- 
lecting and  preserving  them.  Jordan's  "Manual  of 
Vertebrates  "  gives  keys  and  short  descriptions  of  the 
birds  found  east  of  the  Missouri  River;  Chapman's 
"  Handbook  of  the  Birds  of  Eastern  North  America  "  is 
excellent.  To  be  able  to  use  these  manuals  it  is  neces- 
sary to  have  the  bird's  body  in  hand;  and  that  means 
usually  death  for  the  bird.  Recently  there  have  been 
published  several  bird-keys  which  attempt  to  make  it 
possible  to  determine  species,  the  commoner  ones  at  any 
rate,  without  such  close  examination.  The  birds  in  these 
books  are  usually  grouped  wholly  artificially  (without  any 
reference  to  their  natural  relationships)  according  to  such 
salient  characteristics  as  color,  markings,  size,  habit  of 
perching,  or  running,  or  flying,  etc.  Tliese  characteris- 
tics are  such  as  can  presumably  be  made  out  in  the  living 


360 


ELEMENTARY   ZOOLOGY 


bird  by  aid  of  an  opera-glass  or  often  with  the  unaided  eye. 
Such  books  make  no  pretence  to  be  scientific  manuals  nor 
to  include  any  but  the  more  usual  and  strongly  marked 
species.  They  are  usually  limited  to  the  birds  of  a 
restricted  region.  Such  books  are  readily  obtainable. 
There  are  several  popular  illustrated  "bird-magazines" 
devoted  to  accounts  of  the  life  and  habits  of  birds.  Of 
these  "  Bird-lore  "  is  the  organ  of  the  Audubon  Society 
for  the  Protection  of  Birds. 


FIG.  142. — Western  chipping  sparrow,  Spizella  sodalis  arizonae, 
graph  from  life  by  Eliz.  and  Jos.  Grinnell.) 


(Photo- 


In  trying  to  become  acquainted  with  the  birds  of  a 
locality  it  must  be  borne  in  mind  that  the  bird-fauna  of 
any  region  varies  with  the  season.  Some  birds  live  in  a 
certain  region  all  the  year  through;  these  are  called  resi- 
dents. Some  spend  only  the  summer  or  breeding  season 
in  the  locality,  coming  up  from  the  South  in  spring  and 
flying  back  in  autumn  ;  these  are  summer  residents.  Some 
spend  only  the  winter  in  the  locality,  coming  down  from 


BRANCH  CtfORDATA;   CLASS  AYES:    THE  BIRDS       361 

lie  severer  North  at  the  beginning  of  winter  and  going 
>ack  with  the  coming  of  spring;  these  are  winter  resi- 
ients.  Some  are  to  be  found  in  the  locality  only  in  spring 
ind  autumn  as  they  are  migrating  north  and  south 
>etween  their  tropical  winter  quarters  and  their  northern 
lummer  or  breeding  home;  these  are  migrants.  And 
mally  an  occasional  representative  of  certain  bird  species 
vhose  normal  habitat  does  not  include  the  given  locality 
it  all  will  appear  now  and  then  blown  aside  from  its 
•egular  path  of  migration  or  otherwise  astray;  these  are 
visitants.  As  to  the  relative  importance,  numerically, 
>f  these  various  categories  among  the  birds  which  may  be 
bund  in  a  certain  region  and  thus  form  its  bird-fauna  we 
nay  illustrate  by  reference  to  a  definite  region.  Of  the 
551  species  of  birds  which  have  been  found  in  the  State 
>f  Kansas  (a  region  without  distinct  natural  boundaries 
ind  fairly  representative  of  any  Mississippi  valley  region 
)f  similar  extent),  51  are  all-year  residents;  125  are 
;ummer  residents;  36  are  winter  residents;  104  are 
nigrants,  and  35  are  rare  visitants. 

It  must  also  be  kept  in  mind  in  using  bird-keys  and 
lescriptions  to  determine  species  that  the  descriptions  and 
:eys  refer  to  adult  birds,  and  in  ordinary  plumage. 
\mong  numerous  birds  the  young  of  the  year,  old  enough 
o  fly  and  as  large  as  the  adults,  still  differ  considerably 
n  plumage  from  the  latter;  males  differ  from  females, 
nd  finally  both  males  and  females  may  change  their 
dumage  (hence  color  and  markings)  with  the  season, 
[he  seasonal  changes  of  plumage  accomplished  by  molt- 
ng  may  be  marked  or  hardly  noticeable.  "All  birds 
;et  new  suits  at  least  once  a  year,  changing  in  the  fall. 
»ome  change  in  the  spring  also,  either  partially  or  wholly, 
,Thile  others  have  as  many  as  three  changes — perhaps,  to 
slight  extent,  a  few  more.  ...  It  is  claimed  by  some 
bat  now  all  new  colors  are  acquired  by  molt,  and  by 


362  ELEMENTARY  ZOOLOGY 

others  that  in  some  instances  (young  hawks)  an  infusion 
or  loss,  as  the  case  may  be,  of  pigment  takes  place  as  the 
feather  forms,  and  continues  so  long  as  it  grows." 

There  is  much  lack  and  uncertainty  of  knowledge  con- 
cerning the  molting  and  change  of  plumage  by  birds,  and 
careful  observations  by  bird-students  should  be  made  on 
the  subject. 

In  connection  with  learning  the  different  kinds  of  birds 
in  a  locality,  together  with  their  names,  observations 
should  be  made,  and  notes  of  them  recorded,  on  their 
habits  and  on  the  relation  or  adaptation  of  structure  and 
habit  to  the  life  of  the  bird.  Some  of  the  special  subjects 
for  such  observation  are  pointed  out  in  the  following 
paragraphs.  A  suggestive  book,  treating  of  the  adapt- 
ive structure  and  the  life  of  birds  is  Baskett's  "The 
Story  of  the  Birds." 

Bills  and  feet. — The  interesting  adaptation  of  struc- 
ture to  special  use  is  admirably  shown  in  the  varying 
character  of  the  bills  and  feet  of  birds.  The  various  feed- 
ing habits  and  uses  of  the  feet  of  different  birds  are  readily 
observed,  and  the  accompanying  modification  of  bills 
and  feet  can  be  readily  seen  in  birds  either  freshly  killed 
or  preserved  as  "bird-skins."  Such  skins  may  be  made 
as  directed  on  p.  467,  or  may  be  bought  cheaply  of 
taxidermists.  A  set  of  such  skins,  properly  named,  will 
be  of  great  help  in  studying  birds,  and  should  be  in  the 
high-school  collection.  In  some  cases  the  general  struc- 
ture of  feet  and  bills  may  be  seen  in  the  live  birds  by  the 
use  of  an  opera-glass.  The  characters  of  bills  and  feet 
are  much  used  in  the  classification  of  birds,  so  that  any 
knowledge  of  them  gained  primarily  in  the  study  of 
adaptations  will  have  a  secondary  use  in  classification  work. 

Note  the  foot  of  the  robin,  bluebird,  catbird,  wrens, 
warblers  and  other  passerine  or  perching  birds.  It  has 
three  unwebbed  toes  in  front,  and  a  long  hind  toe  per- 


BRANCH  CHORDATA;   CLASS  AYES:   THE  BIRDS      363 

fectly  opposable  to  the  middle  front  one.  This  is  the 
perciiing  foot.  Note  the  so-called  zygodactyl  foot  of  the 
woodpecker,  with  two  toes  projecting  in  front  and  partly 
yoked  together,  and  two  similarly  yoked  projecting 
behind.  Note  the  webbed  swimming  foot  of  the  aquatic 
birds;  note  the  different  degrees  of  webbing,  from  the 
totipalmate,  where  all  four  toes  are  completely  webbed, 
palmate,  where  the  three  front  toes  only  are  bound 


CK 


FIG.  143. — Russet-backed  thrush,  Turdus  ttstulatus.     (Photograph  from 
life  by  Eliz.  and  Jos.  Grinnell.) 

together  but  the  web  runs  out  to  the  claws,  to  the  semi- 
baluiate,  where  the  web  runs  out  only  about  half  way. 
Note  the  lobate  foot  of  the  coots  and  phalaropes.  Note 
the  long  slender  wading  legs  of  the  sandpipers,  snipe 
and  other  shore  birds ;  the  short  heavy  strong  leg  of  the 
divers;  the  small  weak  leg  of  the  swifts  and  humming 
birds,  almost  always  on  the  wing;  the  stout  heavily  nailed 
foot  of  the  scratchers,  as  the  hens,  grouse,  and  turkeys; 
and  the  strong  grasping  talons,  with  their  sharp  long 


364  ELEMENTARY  ZOOLOGY 

curving  nails,  of  the  hawks  and  owls  and  other  birds  of 
prey.  In  all  these  cases  the  fitness  of  the  structure  of  the 
foot  to  the  special  habits  of  the  bird  is  apparent. 

Similarly  the  shape  and  structural  character  of  the  bill 
should  be  noted,  as  related  to  its  use,  this  being  chiefly  con- 
cerned of  course  with  the  feeding  habits.  Note  the  strong 
hooked  and  dentate  bill  of  the  birds  of  prey;  they  tear 
their  prey.  Note  the  long  slender  sensitive  bill  of  the 
sandpipers ;  they  probe  the  wet  sand  for  worms.  Note 
the  short  weak  bill  and  wide  mouth  of  the  night-hawk 
and  whippoorwill  and  of  the  swifts  and  swallows;  they 
catch  insects  in  this  wide  mouth  while  on  the  wing.  Note 
the  flat  lamellate  bill  of  the  ducks;  they  scoop  up  mud 
and  water  and  strain  their  food  from  it.  Note  the  firm 
chisel-like  bill  of  the  woodpeckers;  they  bore  into  hard 
wood  for  insects.  Note  the  peculiarly  crossed  mandibles 
of  the  cross-bills ;  they  tear  open  pine-cones  for  seeds. 
Note  the  long  sharp  slender  bill  of  the  humming-birds; 
they  get  insects  from  the  bottom  of  flower-cups.  Note 
the  bill  and  foot  of  any  bird  you  examine,  and  see  if  they 
are  specially  adapted  to  the  habits  of  the  bird. 

The  tongues  and  tails  of  birds  are  two  other  structures 
the  modifications  and  special  uses  of  which  may  be  readily 
observed  and  studied.  Note  the  structure  and  special  use 
of  the  tongue  and  tail  of  the  woodpeckers;  note  the 
tongue  of  the  humming-bird ;  the  tail  of  the  grackles. 

Flight  and  songs. — The  most  casual  observation  of 
birds  reveals  differences  in  the  flight  of  different  kinds,  so 
characteristic  and  distinctive  as  to  give  much  aid  in 
determining  the  identity  of  birds  in  nature.  Note  the 
flight  of  the  woodpeckers ;  it  identifies  them  unmistakably 
in  the  air.  Note  the  rapid  beating  of  the  wings  of  quail 
and  grouse;  also  of  wild  ducks;  the  slow  heavy  flapping 
of  the  larger  hawks  and  owls  and  of  the  crows ;  and  the 
splendid  soaring  of  the  turkey-buzzard  and  of  the  gulls. 


BRANCH  CHORD  AT  A;  CLASS 


THE  BIRDS     365 


'his  soaring  has  been  the  subject  of  much  observation 
nd  study  but  is  still  imperfectly  understood.  The  soaring 
ird  evidently  takes  advantage  of  horizontal  air-currents, 
nd  some  observers  maintain  that  upward  currents  also 
lust  be  present.  The  principal  hopes  for  the  invention 
f  a  successful  flying-machine  rest  on  the  power  of  soaring 
ossessed  by  birds.  The  speed  of  flight  of  some  birds  is 
normous,  the  passenger-pigeon  having  been  estimated 


%IG.  144. — Oriole's  nest  with  skeleton  of  blue  jay  suspended  from  it;  the 
blue  jay  probably  came  to  the  nest  to  eat  the  eggs,  became  entangled 
in  the  strings  composing  the  nest,  and  died  by  hanging.  (Photograph 
by  S.  J.  Hunter.) 

o  attain  a  speed  of  one  hundred  miles  an  hour.  The 
ong  distances  covered  in  a  single  continuous  flight  by 
ertain  birds  are  also  extraordinary,  as  is  also  the  total 
listance  covered  by  some  of  the  migrants.  "It  is  said 
hat  some  plovers  that  nest  in  Labrador  winter  in  Pata- 
gonia, their  long  wings  easily  carrying  them  this  great 
listance." 


366  ELEMENTARY  ZOOLOGY 

Varying  even  more  than  the  mariner  and  power  of 
flight  among  different  birds  are  the  vocal  utterances,  the 
cries  and  calls  and  singing.  By  their  calls  and  songs 
alone  many  birds  may  be  identified  although  they  remain 
unseen.  The  field-student  of  birds  comes  to  know  them 
by  their  songs;  knows  what  birds  they  are;  knows  what 
they  are  doing  or  not  doing;  knows  what  time  in  their 
life-season  it  is,  whether  they  are  mating,  or  brooding,  or 
preparing  to  migrate;  knows  whether  they  are  frightened, 
or  self-confident,  whether  in  distress  or  happy.  Little 
urging  and  suggestion  are  needed  to  induce  the  student 
to  attend  to  the  songs.  But  the  naturalist  should  not 
only  hear  and  enjoy  them,  but  by  observation  and  the 
recording  of  repeated  observations,  he  should  come  to 
understand  the  significance  of  the  calls  and  songs. 

As  to  how  these  sounds  are  made,  attention  has  already 
been  called  (see  p.  338)  to  the  voice-organ  or  syrinx. 
The  condition  of  this  organ  varies  much  in  birds,  as 
would  be  expected  from  the  differing  character  of  vocal 
utterances.  Dissections  will  make  these  differences 
apparent. 

Nesting  and  care  of  young. — Among  the  birds'  most 
interesting  instincts  and  habits  are  those  domestic  ones 
which  include  mating,  nest-building,  and  care  of  the 
young.  Birds'  eggs  and  birds'  nests  are  always  attrac- 
tive objects  of  search  and  collection  for  boys,  and  most 
boys  have  a  considerable  personal  knowledge  of  the 
domestic  habits  of  the  commoner  summer  birds  of  their 
region.  With  this  interest  and  unsystematized  knowledge 
as  a  basis  the  teacher  should  be  able  to  get  from  the  class 
much  excellent  field-work  and  personal  observation.  The 
first  thing  to  undertake  in  this  study  is  the  gathering  of 
data  regarding  the  character  of  the  nests  of  different 
species,  their  situation,  the  time  of  nesting,  the  participa- 
tion or  non-participation  of  the  male  in  nest-building, 


BRANCH   CHORD  AT  A;   CLASS  AYES:    THE  BIRDS       367 

etc. ;  also  the  number  of  eggs,  their  size  and  color  mark- 
ings, the  length  of  incubation,  the  help  or  lack  of  help  of 
the  male  in  brooding,  etc.  In  connection  with  this 
gathering  of  data  in  the  field  by  note-taking,  sketching, 
and  photographing,  nests  and  eggs  can  be  collected  (see 
directions  on  page  469).  Let  only  one  clutch  of  eggs  cf 
each  species  be  taken  for  the  common  high-school  collec- 
tion, and  if  more  than  one  nest  is  desired  take  used  and 
deserted  nests.  When  the  nestlings  are  hatched,  the 
bringing  of  food,  the  defence  of  the  home,  and  the  teach- 
ing of  the  young  to  fly  should  all  be  observed  and  noted. 

Some  attempt  should  be  made  to  systematize  the  mis- 
cellaneous data  obtained.  Do  all  the  members  of  a  group 
have  similar  nesting  habits  ?  Note  the  early  nesting  of 
birds  of  prey ;  note  the  nests  of  the  woodpeckers  in  holes 
in  trees ;  note  the  nesting  of  the  various  swallows.  Is 
there  any  significance  in  the  colors  and  markings  of  eggs  ? 
Observe  the  protective  coloration  obvious  in  some  (see 
Chap.  XXXI).  Are  there  differences  in  the  condition  of 
the  newly  hatched  nestlings  ?  Note  the  helpless  altricial 
young  of  the  robin ;  the  independent  precocial  young  of 
the  quail. 

The  strong  influence  of  the  mating  passion  will  be 
made  plain  by  observations  on  the  fighting,  love-making, 
singing,  and  general  behavior  of  the  birds  in  the  mating 
season.  The  expression  of  the  mental  and  emotional 
traits,  the  psychic  phenomena  of  birds,  are  most  empha- 
sized at  this  time,  and  reveal  the  possession  among 
animals  lower  than  man  of  many  characteristics  which  are 
too  commonly  ascribed  as  the  exclusive  attributes  cf  the 
human  species. 

Local  distribution  and  migration. — As  explained  in 
Chapter  XXXII,  the  geographical  distribution  of  animals 
is  a  subject  of  much  importance,  and  offers  good  oppor- 
tunities in  its  more  local  features  for  student  field-work. 


368  ELEMENTARY  ZOOLOGY 

The  field-study  of  the  birds  of  a  given  locality  will  comprise 
much  observation  bearing  directly  on  zoogeography  or 
the  distribution  of  animals.  Certain  birds  will  be  found 
to  be  limited  to  certain  parts  of  even  a  small  region,  the 
swimmers  will  be  found  in  ponds  and  streams  and  the 
long-legged  shore-birds  on  the  pond-  or  stream-banks,  or 
in  the  marshes  and  wet  meadows,  although  a  few  like  the 


FIG.  145. — Western  robin,  Merula  migratoria  propinqua.   (Photograph  from 
life  by  Eliz.  and  Jos.  Grinnell.) 

upland  plover,  curlews,  and  godwits  are  common  on  the 
dry  upland  pastures.  Distinguish  the  ground-birds  from 
the  birds  of  the  shrubs  and  hedge-rows  and  these  again 
from  the  strictly  forest-birds.  Find  the  special  haunts  of 
swallows  and  kingfishers.  Which  are  the  shy  birds 
driven  constantly  deeper  into  the  wild  places  or  being 
exterminated  by  the  advance  of  man ;  which  birds  do  not 


BRANCH   CHORD  AT  A;   CLASS  AYES:    THE  BIRDS       369 

retreat  but  even  find  an  advantage  irf  man's  seizure  of  the 
land,  obtaining  food  from  his  fields  and  gardens  ? 

Make  a  map  on  large  scale  of  the  locality  of  the  school, 
showing  on  it  the  topographic  features  of  the  region,  such 
as  streams,  ponds,  marshes,  hills,  woods,  springs,  wild 
pastures,  etc.,  also  roads  and  paths,  and  such  landmarks 
as  schoolhouses,  county  churches,  etc.  On  this  map  in- 
dicate the  local  distribution  of  the  birds,  as  determined 
by  the  data  gradually  gathered;  mark  favorite  nesting- 
places  of  various  species,  roosting-places  of  crows  and 
blackbirds,  feeding-places,  and  bathing-  and  drinking- 
places  of  certain  kinds,  the  exact  spots  of  finding  rare 
visitants,  rare  nests,  etc.,  etc.  The  making  of  such  a 
zoogeographical  map  will  be  a  source  of  great  interest 
and  profit  to  the  students. 

As  already  mentioned,  many  of  the  birds  of  a  locality 
are  "migrants,"  that  is,  they  breed  farther  north,  but 
spend  the  winter  in  more  southern  latitudes.  These 
migrants  pass  through  the  locality  twice  each  year,  going 
north  in  the  spring  and  south  in  the  autumn.  They  are 
much  more  likely  to  be  observed  during  the  spring  migra 
tion  than  in  the  fall,  as  the  flight  south  is  usually  more 
hurried.  The  observation  of  the  migration  of  birds  is 
very  interesting,  and  much  can  be  done  by  beginning 
students.  Notes  should  be  made  recording  the  first  time 
each  spring  a  migrating  species  is  seen,  the  time  when  it 
is  most  abundant  and  the  last  time  it  is  seen  the  same 
spring.  Similar  records  should  be  made  showing  the 
movements  of  the  birds  in  the  fall.  A  series  of  such 
records  covering  a  few  years  will  show  which  are  the 
earliest  species  to  appear,  which  the  later,  and  which  the 
last.  Such  records  of  appearance  and  disappearance 
should  also  be  kept  for  the  summer  residents,  those  birds 
that  come  from  the  South  in  the  spring,  breed  in  the 
locality,  and  then  depart  for  the  South  again  in  the 


37°  ELEMENTARY  ZOOLOGY 

autumn.  Notes  on  the  kinds  of  days,  as  stormy,  clear, 
cold,  warm,  etc.,  on  which  the  migration  seems  to  be 
most  active ;  on  the  greater  prevalence  of  migratory  flights 
by  day  or  by  night;  on  the  height  from  the  earth  at  which 
the  migrants  fly,  etc.,  are  all  worth  while.  The  Division 
of  Biological  Survey,  U.  S.  Department  of  Agriculture, 
keeps  records  of  notes  on  migration  sent  in  by  voluntary 
observers  and  furnishes  blanks  to  be  filled  out  by  each 
observer.  A  suggestive  book  about  migration,  and  one 
giving  the  records  for  many  species  at  many  points  in  the 
Mississippi  valley  is  Cooke's  "Bird  Migration  in  the 
Mississippi  Valley."  Migration  is  discussed  in  most  bird- 
books. 

Feeding  habits,  economics,  and  protection  of  birds.— 
The  feeding  habits  of  birds  are  not  only  interesting,  but 
their  determination  decides  the  economic  relation  of  birds 
to  man,  that  is,  whether  a  particular  bird  species  is  harm- 
ful or  beneficial  to  man.  Casual  observation  shows  that 
birds  eat  worms,  grains,  seeds,  fruits,  insects.  A  single 
species  often  is  both  fruit-eating  and  insect-eating.  Do 
fruits  or  do  insects  compose  the  chief  food -supply  of  the 
species  ?  To  determine  this  more  than  casual  observation 
is  necessary.  The  birds  must  be  watched  when  feeding 
at  different  seasons.  The  most  effective  way  of  determin- 
ing the  kind  of  food  which  the  bird  takes  is  to  examine 
the  stomachs  of  many  individuals  taken  at  various  times 
and  localities.  Much  work  of  this  kind  has  been  clone, 
especially  by  the  investigators  connected  with  the  Division 
of  Biological  Survey  of  the  U.  S.  Department  of  Agricul- 
ture, and  pamphlets  giving  the  results  of  these  investiga- 
tions can  be  had  from  the  Division.  It  has  been  distinctly 
shown  that  a  great  majority  of  birds  are  chiefly  beneficial 
to  man  by  eating  noxious  insects  and  the  seeds  of  weeds. 
Many  birds  commonly  reputed  to  be  harmful,  and  for  that 
reason  shot  by  farmers  and  fruit-growers,  have  been 


BRANCH  CHORD  AT  A  ;  CLASS 


THE  BIRDS     371 


proved  to  do  much  more  good  than  harm.  Some  few 
birds  have  been  proved  to  be,  on  the  whole,  harmful. 
An  investigation  of  the  food  habits  of  the  crow,  a  bird  of 
ill-repute  among  farmers,  based  on  an  examination  of  909 
stomachs  shows  that  about  29  per  cent  of  the  food  for  the 


FlG.   146. — Sickle-billed  thrasher,  Harporhynchus  redevivus. 
from  life  by  Eliz.  and  Jos.  Grinnell.) 


(Photograph 


year  consists  of  grain,  of  which  corn  constitutes  something 
more  than  21  per  cent,  the  greatest  quantity  being  eaten 
in  the  three  winter  months.  All  of  this  must  be  either 
waste  grain  picked  up  in  fields  and  roads,  or  corn  stolen 
from  cribs  and  shocks.  May,  the  month  of  sprouting  corn, 


372  ELEMENTARY  ZOOLOGY 

shows  a  slight  increase  over  the  other  spring  and  summer 
months.  On  the  other  hand  the  loss  of  grain  is  offset  by 
the  destruction  of  insects.  These  constitute  more  than 
23  per  cent  of  the  crow's  yearly  diet,  and  the  larger  part 
of  them  are  noxious.  The  remainder  of  the  crow's  food 
consists  of  wild  fruit,  seeds  and  various  animal  substances 
which  may  on  the  whole  be  considered  neutral. 

The  slaughter  of  birds  for  millinery  purposes  has 
become  so  fearful  and  apparent  in  recent  years  that  a 
strong  movement  for  their  protection  has  been  inaugu- 
rated. Rapacious  egg-collecting,  legislation  against 
birds  wrongly  thought  to  be  harmful  to  grains  and  fruit, 
and  the  selfish  wholesale .  killing  of  birds  by  professional 
and  amateur  hunters,  help  in  the  work  of  destruction. 
Apart  from  the  brutality  of  such  slaughter,  and  the  ex- 
termination of  the  most  beautiful  and  enjoyable  of  our 
animal  companions,  this  destruction  *  works  strongly 
against  our  material  interests.  Birds  are  the  natural 
enemies  of  insect  pests,  and  the  destroying  of  the  birds 
means  the  rapid  increase  and  spread,  and  the  enhanced 
destructive  power  of  the  pests.  It  is  asserted  by  investi- 
gators that  during  the  past  fifteen  years  the  number  of  our 
common  song-birds  has  been  reduced  to  one-fourth.  At 
the  present  rate,  says  one  author,  extermination  of  many 
species  will  occur  during  the  lives  of  most  of  us.  Already 
the  passenger-pigeon  and  Carolina  paroquet,  only  a  few 
years  ago  abundant,  are  practically  exterminated.  Protect 
the  birds ! 

*  One  of  the  most  unfortunate  and  conspicuous  examples  of  this  slaughter 
is  the  partial  extermination  of  the  song-birds  of  Japan  in  the  interests  of 
European  milliners.  To  meet  their  demands  the  country  people  used  bird- 
lime throughout  the  woods  with  disastrous  effectiveness,  as  shown  in  the 
present  exceeding  scarcity  of  birds  and  the  abundance  of  insect  pests. 


CHAPTER    XXVIII 

BRANCH  CHORDATA  (Continued^    CLASS  MAM- 
MALIA:   THE    MAMMALS 

THE    MOUSE   (Mas  musculus) 

TECHNICAL  NOTE. — It  is  best  to  catch  specimens  alive  in  a  good 
trap.  A  live  trap  well  baited  and  placed  in  some  old  granary 
should  furnish  plenty  for  class  use.  White  mice  can  often  be  ob- 
tained at  "  bird-stores."  When  mice  are  not  procurable,  use  rats. 
A  rat  is  perhaps  preferable  on  account  of  its  size,  but  all  essential 
structures  can  readily  be  made  out  in  the  mouse.  Specimens 
should  be  killed  by  chloroform  as  described  for  the  toad,  p.  5. 

Structure  (fig.  147). —  Compare  the  external  characters 
of  the  mouse  with  those  of  the  toad  and  sparrow.  The 
mouse,  unlike  the  other  vertebrates  so  far  studied,  is  thickly 
covered  with  hair  all  over  its  body  except  on  the  tip  -of 
the  nose  and  the  soles  of  the  feet.  Where  are  the  nostrils 
placed  ?  What  are  the  large  leaf-like  expansions  called 
pinna  situated  just  back  of  the  eyes  ?  Pull  open  the 
mouth  and  note  the  large  incisor  teeth  on  the  upper  and 
lower  jawrs.  Cut  one  corner  of  the  mouth  back  and 
observe  the  large  flat-topped  molar  teeth  on  both  jaws. 
How  does  the  attachment  of  the  large  fleshy  tongue  differ 
from  the  condition  in  the  toad  ?  The  toad's  tongue  is  for 
snapping  up  insects,  whereas  in  the  mouse  this  organ 
serves  to  move  food  about  in  the  mouth.  On  the  tongue 
are  numerous  small  taste-papilla.  Notice  the  long  hairs, 
"  feelers,"  on  each  side  of  the  nose.  Note  the  similarity 
between  the  front  paws  and  our  own  hands ;  each  has 
four  fingers  with  a  small  rudimentary  thumb  on  the  inner 

373 


374  ELEMENTARY  ZOOLOGY 

side  of  the  paw.  How  does  the  hind  foot  of  the  mouse 
differ  from  the  foot  of  man  ?  Posteriorly  the  body  is 
terminated  by  a  long  tail.  At  the  root  of  the  tail  is  a 
small  aperture,  the  amis,  and  just  below,  or  ventral  to  it, 
is  the  opening  from  the  kidneys  and  reproductive  organs. 

TECHNICAL  NOTE. — Place  the  mouse  on  its  back  in  a  dissecting- 
pan  and  cut  through  the  skin  from  anus  to  the  lower  jaw.  Extend 
the  legs,  pin  down  each  foot  and  pin  out  the  cut  edges  of  the 
skin.  Now  carefully  cut  forward  through  the  body-wajl  from  the 
anal  region  and  on  through  the  breast-bones  and  ribs.  Pin  each 
side  out. 

Near  the  hindmost  pair  of  ribs  note  a  sheet  of  muscles, 
the  diaphragm,  which  extends  across  the  body-cavity, 
dividing  it  into  an  anterior  portion,  the  thoracic  cavity, 
and  a  posterior,  the  abdominal  cavity.  What  are  the  most 
conspicuous  organs  in  the  thoracic  cavity  ?  Leading 
anteriorly  to  the  mouth-cavity  is  a  long  tube,  the  trachea, 
composed  of  a  series  of  cartilaginous  parts  of  rings  placed 
end  to  end.  Note  at  its  anterior  end  the  glottis  and 
epiglottis.  Insert  a  blowpipe  into  the  glottis  and  inflate 
the  lungs,  which  will  fill  all  the  otherwise  unfilled  space 
in  the  thoracic  cavity.  The  abdominal  cavity  contains 
the  viscera  suspended  in  a  fold  of  the  lining  membrane,  as 
in  the  other  vertebrates  studied.  Note  lying  against  the 
diaphragm  a  large,  red,  glandular  structure,  the  liver. 
Separate  the  two  large  lobes  of  the  liver  and  expose  the 
opalescent  gall-bladder.  By  passing  a  canula  into  this 
and  ligaturing,  the  cystic  duct  may  be  injected.  Beneath 
the  liver  is  a  large  loop-shaped  expansion  of  the  alimen- 
tary canal,  the  stomach.  Arising  from  the  right  end  of 
the  stomach  is  the  narrow  duodenum,  which  gradually 
merges  into  the  very  much  convoluted  small  intestine,  or 
ileum,  which  is  followed  by  the  large  intestine,  or  colon, 
the  last  part  of  which  is  a  straight  tube,  the  rectum.  The 
small  intestine  occupies  most  of  the  space  in  the  peri- 


BRANCH  CHORD  AT  A:   CLASS  MAMMALIA  375 

toneal  cavity.  Within  the  loop  of  the  pylorus  will  be 
found  an  irregular  pinkish  mass  of  tissue,  the  pancreas. 
Beneath  the  stomach  on  the  left  side  of  the  body  lies  a 
very  dark  glandular  mass  not  much  unlike  the  liver  but 
altogether  detached  from  it.  This  structure  is  the  spleen, 
a  ductless  gland. 

Note  dorsally  of  the  trachea  a  long  tube  passing  through 
the  diaphragm  and  connecting  the  mouth  with  the 
stomach.  What  is  this  tube  ?  Note  the  Eustachian  tubes 
extending  from  the  mouth  to  the  ears.  The  median  part 
of  the  roof  of  the  mouth  is  the  palate,  hard  in  front,  soft 
behind.  A  pair  of  small  bodies  at  the  sides  of  the  soft 
palate  near  its  hinder  end  are  the  tonsils.  At  the  pos- 
terior angle  of  the  lower  jaw  are  glandular  bodies,  the  sub- 
maxillary  glands,  which  lead  by  a  short  duct  anteriorly 
to  open  on  the  floor  of  the  mouth.  On  the  sides  of  the 
neck  just  below  the  ears  are  pink  or  yellowish  bodies,  the 
parotid  glands,  opening  anteriorly  in  the  sides  of  the 
mouth-cavity.  These  two  sets  of  glands  are  collectively 
known  as  the  salivary  glands,  the  function  of  which  is  to 
secrete  the  saliva.  Push  apart  the  sub-maxillary  glands 
and  note  below  them  overlying  the  trachea  on  either  side 
two  dark-red  lobes  connected  by  a  band  of  tissue.  These 
constitute  the  thyroid  gland,  another  of  the  so-called 
ductless  glands.  Within  the  thoracic  cavity  anterior  to 
the  heart  note  a  mass  of  pinkish  tissue,  the  thymus  gland. 
Observe  the  large  masseter  muscles,  which  cover  the  jaws. 
What  is  their  function  ?  On  either  side  of  the  neck  lies  a 
large  blood-vessel,  the  external  jugular  vein,  which  col- 
lects blood  from  the  head  and  carries  it  down  to  the  heart. 
Note  the  large  pectoral  muscles  which  cover  the  breast  and 
extend  out  into  the  arms,  and  which  are  so  strong  and 
highly  developed  in  the  sparrow.  The  head  is  supported 
by  large  muscles  which  run  down  the  back  of  the  neck 
to  the  ribs.  Others  are  attached  to  the  ribs,  which  they 


376 


ELEMENTARY  ZOOLOGY 


raise  and  lower.  These  movements,  together  with  the 
contraction  of  the  diaphragm,  cause  the  expansion  and 
contraction  of  the  thoracic  cavity 
whereby  the  lungs  are  regularly  filled 
and  emptied.  Note  that  the  abdomen 
is  covered  by  a  double  layer  of  mus- 
cular tissue,  the  outer  part  made  up 
of  the  external  oblique  muscles,  the 
inner  by  the  internal  oblique  muscles. 
Examine  the  heart.  How  many 
auricles  has  it  ?  The  ventricles  in 
the  mouse,  as  in  the  bird,  are  entirely 
separated,  forming  two  complete 
compartments,  a  right  and  a  left 
ventricle.  The  blood  flowing  from 
the  veins  of  the  body  is  collected  in 
the  right  auricle,  thence  it  passes  into 
the  right  ventricle,  whence  it  is  con- 
veyed to  the  lungs  ;  returning  it  flows 
through  the  left  auricle  into  the  left 
ventricle,  whence  it  is  forced  through 
the  arteries  of  the  body.  For  a 
study  of  the  circulatory  system  in 
mammals  (fig.  148),  a  rat  or  a  rabbit 
should  be  injected  by  the  teacher  and 
an  advanced  text-book,  as  Parker's 
1 '  Zootomy  ' '  or  Marshall  and  Hurst's 
'  used  as  a  guide.  A  sheep's  heart 
is  very  good  to  cut  open  for  a  class  demonstration. 

Make  a  drawing  of  the  organs  observed  thus  far  in  the 
dissection. 

The  kidneys  in  the  mouse  are  situated  in  the  dorsal 
region  next  to  the  backbone.  They  consist  of  two  bean- 
shaped  smooth  glands.  From  them  a  pair  of  ducts,  the 
ureters,  can  be  traced  down  to  a  median  thin-wallecl 


FIG.  148.  —  Diagram  of 
the  circulation  of  the 
blood  in  a  mammal;  a, 
auricles  ;  /,  lung  ;  Iv, 
liver;  /,  portal  vein 
bringing  blood  from  the 
intestine;  v,  ventricles; 
the  arrows  show  the  di- 
rection of  the  current; 
the  shaded  vessels 
carry  venous  blood,  the 
others  arterial  blood. 
(From  Kingsley.) 

"  Practical  Zoology 


BRANCH  CHORD  AT  A:   CLASS   MAMMALIA 


37' 


muscular  sac,  the  bladder.  The  bladder  opens  to  the 
exterior  of  the  body  by  means  of  a  short  tube,  the 
tiretJira.  Cut  open  a  kidney  longitudinally  and  examine 
the  cut  surfaces. 

The  two  egg-glands  of  the  female  mouse  lie  in  the 
median  portion  of  the  abdominal  cavity,  somewhat  below 
the  kidneys,  and  from  the  vicinity  of  each  runs  an  egg- 
tube.  These  tubes  meet  below  the  bladder,  and  open  to 
the  exterior  of  the  body  through  the  aperture  noted  below 
the  anus.  In  the  posterior  parts  of  these  tubes  lie  until 
birth  the  developing  embryos. 

TECHNICAL  NOTE. — Fora  study  of  the  nervous  system  place  the 
specimen  ventral  side  down  and  cut  through  the  skull  with  the  bone- 
cutters  or  heavy  scissors,  exposing  the  brain  and  spinal  cord. 

Note  the  large  bruin  (fig.  149),  composed  of  small  optic 
lobes,  large  cerebrum,  cerebellum,  and  medulla  oblongata, 
followed  by  the  long  spinal  cord.  Note  the  nerves  aris- 
ing from  the  brain  and  spinal  cord. 

For  a  careful  dissection  of  the  mammalian  nervous 
system  a  larger  mammal,  such  as  a  cat  or  dog  or  rabbit, 
should  be  used.  For  guide  use  a  text-book  such  as,  for 
the  dog,  Howell's  "Dissection  of  the  Dog  "  ;  for  the  cat, 
Reighard  and  Jennings'  "  Anatomy  of  the  Cat  "  ;  and  for 
the  rabbit,  Parker's  "  Zootomy  "  or  Marshall  and  Hurst's 

Sunfish  Toad          Snake  Sparrow  Mouse 


Sp.  Cd. 


Fir,.  149.  -Diagram  of  brains  of  vertebrates;   Olf.  L.,  olfactory  lobes-   Cbr 
cerebrum  ;  Md.  Br.,  midbrain  (optic  lobes)  ;  CbL,  cerebellum  ;'  Med. 
Ol>.,  medulla  oblongata ;   Sp.  Cd.,  spinal  cord.     (From  specimens.) 


37* 


ELEMENTARY  ZOOLOGY 


' '  Practical  Zoology. ' '  Make  a  good  preparation  of  the 
brain  and  preserve  it  for  future  use  in  some  fluid  like 
Fischer's  fluid  (see  page  453). 

TECHNICAL  NOTE. — Prepare  a  well-cleaned  skeleton  by  boiling  a 
specimen  in  a  soap  solution  and  thoroughly  cleansing  it  (seep.  452). 

Note  the  very  compact  skeleton  of  the  mouse.  Note 
the  closely  sutured  skull.  How  many  cervical  or  neck 
vertebrce  are  there  ?  The  ribs  are  attached  to  the  thoracic 
vertebra.  How  many  pairs  of  ribs  ?  The  bony  thorax 
supports  the  shoulder-girdle  and  bones  of  the  fore  legs. 
The  thorax  is  followed  by  a  series  of  ribless  vertebrae,  the 
lumbar  vertebrce,  which  in  the  posterior  region  of  the  body 
fuse  with  the  pelvic  girdle  supporting  the  hind  limbs. 
The  body  vertebrae  are  succeeded  by  the  very  much 
smaller  caudal  vertebrce.  Compare  the  skeleton  of  the 
mouse  with  that  of  the  bird;  also  with  that  of  the  toad. 
For  directions  for  a  detailed  study  of  the  skeleton  see  in 
Parker's  "  Zootomy  "  an  ac- 
count of  the  skeleton  of  the 
rabbit,  pp.  263-286. 

TECHNICAL  NOTE.  —  For  the 
study  of  the  eye  (fig.  150)  the 
teacher  should  obtain  the  eye  of 
some  large  mammal,  as  the  ox  or 
sheep,  with  which  to  make  a  class 
demonstration.  The  eye  of  a 
rabbit  or  cat  can  of  course  be 
used.  For  an  account  of  the  verte- 
brate eye  see  Parker  and  Haswell's 
"  Text-book  of  Zoology, "  Vol.  II. 
pp.  103-107.  For  a  study  of  the 
ear  use  a  bird  or  mammal,  and 
see  pp.  107-110  of  the  same  book.  FIG.  150.— Diagram  of  vertebrate 


eye;  c,  choroid;  z,  iris;  /,  lens;  n, 
optic  nerve;  r,  retina;  s,  sclerotic. 
(From  Kingsley.) 


Life-history   and   habits. 

— The  house-mouse  is  not  a 

native  of  North  America,   but  was  introduced    into  this 

country  from  Europe,  to  which,  in  turn,  it  came  from  Asia, 


BRANCH   CHORD  AT  A:   CLASS  MAMMALIA  379 

its  original  habitat.  The  mouse  came  to  this  country  in 
the  vessels  of  early  explorers.  Similarly  the  brown  and 
black  rats,  now  so  abundant  all  over  North  America,  and 
members  of  the  same  genus  as  the  mouse,  were  intro- 
duced from  Europe.  Accompanying  man  in  his  travels 
the  mouse  has  spread  from  Asia  until  it  is  now  to  be 
found  over  the  whole  world. 

The  habits  of  mice  are  welt  known ;  their  fondness  for 
living  in  our  homes  and  outbuildings  makes  them  familiar 
acquaintances.  Their  food  is  varied ;  they  seem  to  thrive 
best,  however,  on  a  vegetable  diet.  Grains  and  nuts  are 
favorite  foods.  The  house-cat  is  their  greatest  enemy, 
but  man  takes  advantage  of  their  instinct  to  go  into  holes 
by  constructing  traps  with  funnel  or  tunnel  entrances 
which,  baited  with  cheese  or  other  favorite  food,  are 
fatally  attractive.  In  climbing,  mice  are  aided  by  the 
tail.  Their  strong  hind  legs  enable  them  to  stand  erect, 
and  even  to  take  several  steps  in  this  posture.  They  can 
swim  readily,  although  naturally  they  rarely  take  to 
water.  Their  special  senses  are  keen,  the  senses  of  hear- 
ing and  taste  being  unusually  well  developed.  Their 
"  singing,"  which  has  been  the  subject  of  much  discussion, 
seems  to  be  actually  a  voluntary  and  normal  performance 
which,  however,  hardly  deserves  to  be  called  singing,  but 
rather  a  slightly  varied  peeping  or  whistling. 

The  mouse  is  a  prolific  mammal,  producing  from  four 
to  six  times  a  year  broods  of  from  four  to  eight  young. 
The  mouse  makes  a  cosy  nest  of  straw,  bits  of  paper, 
feathers,  wool  or  other  soft  materials,  and  in  this  the 
young  are  born.  The  newly  born  mice  are  very  small 
and  are  blind  and  helpless.  They  are  odd  little  creatures, 
being  naked  and  almost  transparent.  They  grow  rapidly, 
being  covered  with  hair  in  a  week,  although  not  opening 
their  eyes  for  about  two  weeks.  A  day  or  two  after  their 
eyes  are  open  they  begin  to  leave  the  nest,  and  hunt  for 
food  for  themselves. 


38°  ELEMENTARY  ZOOLOGY 

OTHER    MAMMALS 

The  mammals  constitute  the  highest  group  of  animals, 
including  man,  the  monkeys  and  apes,  the  quadrupeds, 
the  bird-like  bats  and  fish-like  seals  and  whales;  in  all 
about  2500  species.  They  are  found  everywhere  except 
on  a  few  small  South  Sea  islands.  Only  a  few  species, 
however,  have  a  world-wide  distribution.  The  name 
Mammalia  is  derived  from  the  mammary  or  milk  glands 
with  which  the  females  are  provided  and  by  the  secretion 
of  which  the  young  of  this  class,  born  free  in  all  but  a 
few  of  the  lowest  forms,  are  nourished  for  some  time  after 
birth.  In  size  mammals  range  from  the  tiny  pigmy-shrew 
and  harvest  mouse,  which  can  climb  a  stem  of  wheat,  to 
the  great  sulphur-bottom  whale  of  the  Pacific  Ocean,  which 
attains  a  length  of  a  hundred  feet  and  a  weight  of  many 
tons.  Mammals  differ  from  fishes  and  batrachians  and 
agree  with  reptiles  and  birds  in  never  having  external 
gills  ;  they  differ  from  reptiles  and  agree  with  birds  in  being 
warm-blooded  and  in  having  a  heart  with  two  distinct 
ventricles  and  a  complete  double  circulation  ;  finally,  they 
differ  from  both  reptiles  and  birds  in  having  the  skin  more 
or  less  clothed  with  hair,  the  lungs  freely  suspended  in  a 
thoracic  cavity  separated  from  the  abdominal  by  a  mus- 
cular partition,  the  diaphragm,  and  in  the  possession  by 
the  females  of  mammary  glands.  In  economic  uses  to 
man  mammals  are  the  most  important  of  all  animals. 
They  furnish  the  greater  portion  of  the  animal  food  of  many 
human  races,  likewise  a  large  amount  of  their  clothing. 
Horses,  asses,  oxen,  camels,  reindeer,  elephants,  and 
llamas  are  beasts  of  burden  and  draught;  swine,  sheep, 
cattle,  and  goats  furnish  flesh,  and  the  two  latter  milk  for 
food ;  the  wool  of  sheep,  the  furs  of  the  carnivores,  and 
the  leather  of  cattle,  horses,  and  others  are  used  for  cloth- 
ing, while  the  bones  and  horns  of  various  mammals  serve 
various  purposes. 


BRANCH   CHORD  AT  A:   CLASS   MAMMALIA  381 

Body  form  and  structure. — The  mammalian  body 
varies  greatly.  Its  variety  of  form  and  general  organiza- 
tion is  explained  by  the  facts  that,  although  most  of  the 
species  live  on  the  surface  of  the  earth,  some  are  burrowers 
in  the  ground,  some  flyers  in  the  air,  and  some  swimmers 
in  the  water.  Mammals  never  have  more  than  two  pairs 
of  limbs;  in  most  cases  both  pairs  are  well  developed  and 
adapted  for  terrestrial  progression.  In  the  aerial  bats  the 
fore  limbs  are  modified  into  organs  of  flight;  among  the 
aquatic  seals,  sea-lions,  walruses,  and  whales  both  sets  are 
modified  to  be  swimming  flippers  or  paddles.  In  many 
of  these  aquatic  forms  the  hind  limbs  are  greatly  reduced 
or  even  completely  wanting. 

Most  mammals  are  externally  clothed  with  hair,  which 
is  a  peculiarly  modified  epidermal  process.  Each  hair, 
usually  cylindrical,  is  composed  of  two  parts,  a  central  pith 
containing  air,  and  an  outer  more  solid  cortex;  each  hair 
rises  from  a  short  papilla  sunk  at  the  bottom  of  a  follicle 
lying  in  the  true  skin.  In  some  mammals  the  hairs 
assume  the  form  of  spines  or  ' '  quills, ' '  as  in  the  porcupine. 
The  hairy  coat  is  virtually  wanting  in  whales  and  is  very 
sparse  in  certain  other  forms,  the  elephant,  for  example, 
which  has  its  skin  greatly  thickened.  The  claws  of  beasts 
of  prey,  the  hooves  of  the  hoofed  mammals,  and  the  outer 
horny  sheaths  of  the  hollow-horned  ruminants  are  all 
epidermal  structures. 

tThe  bones  of  mammals  are  firmer  than  those  of  other 
vertebrates,  containing  a  larger  proportion  of  salts  of  lime. 
Among  the  different  forms  the  spinal  column  varies  largely 
in  the  number  of  vertebrae,  this  variation  being  chiefly 
due  to  differences  in  length  of  tail.  Apart  from  the 
caudal  vertebrae  their  usual  number  is  about  thirty.  The 
mammalian  skull  is  very  firm  and  rigid,  all  the  bones 
composing  it,  excepting  the  lower  jaw,  the  tiny  auditory 
ossicles,  and  the  slender  bones  of  the  hyoid  arch,  being 


382 


ELEMENTARY  ZOOLOGY 


immovably  articulated  together.  The  correspondence 
between  the  bones  of  the  two  sets  of  limbs  is  very  ap- 
parent. The  number  of  digits  varies  in  different  mammals, 
and  also  in  the  fore  and  hind  limbs  of  a  single  species. 
Among  the  Ungulates  the  reduction  in  the  number  of 
digits  is  especially  noticeable;  the  forefoot  of  a  pig  has 
four  digits,  that  of  the  cow  two,  and  that  of  the  horse  one. 
The  two  short  "  splint  "  bones  in  the  horse  are  remnants 
of  lost  digits.  The  teeth  are  important  structures  in 
mammals,  being  used  not  only  for  tearing  and  masticat- 
ing food,  but  as  weapons  of  offence  and  defence.  A  tooth 
consists  of  an  inner  soft  pulp  (in  old  teeth  the  pulp  may 
become  converted  into  bone-like  material)  surrounded  by 
hard  white  dentine  or  ivory,  which  is  covered  by  a  thin 
layer  of  enamel,  the  hardest  tissue  known  in  the  animal 
body.  A  hard  cement  sometimes  covers  as  a  thin  layer 
the  outer  surface  of  the  root,  and  may  also  cover  the 
enamel  of  the  crown.  The  teeth  in  mcst  forms  are  of 
three  groups:  (a)  the  incisors,  with  sharp  cutting  edges 
and  simple  roots,  situated  in  the  centre  of  the  jaw;  (&)  the 
canines,  often  conical  and  sharp-pointed,  next  to  the 
incisors;  (c)  next  the  molars,  broad  and  flat-topped  for 
grinding,  and  divided  into  premolars  and  true  molars. 
There  is  great  variety  in  the  character  and  arrangement 
of  these  structures  in  mammals,  their  variations  being 
much  used  in  classification.  The  number  and  arrange- 
ment of  the  teeth  is  expressed  by  a  dental  formula,  as,  for 
example,  in  the  case  of  man 

2  —  2        3—3 

=  32. 


2    -  -    2         I    -  -    I      J  2  --  2  3   —   3 

The  mouth  is  bounded  by  fleshy  lips.  On  the  floor  of 
the  mouth  is  the  tongue,  which  bears  the  taste-buds  or 
papillae,  the  organs  of  taste.  The  oesophagus  is  always 
a  simple  straight  tube,  but  the  stomach  varies,  greatly, 


BRANCH  CHORD  AT  A:  CLASS  MAMMALIA 


3*3 


FlG.  151.  — A  group  of  Rocky  Mountain  sheep,  or  ''big  horns,"  Oi'is  cana- 
densis,  including  males,  females  and  young.  (Photograph  "by  E.  Willis 
from  specimens  mounted  by  Prof.  L.  L.  Dyche,  University  of  Kansas.) 


384  ELEMENTARY  ZOOLOGY 

being  usually  simple,  but  sometimes,  as  in  the  ruminants 
and  whales,  divided  into  several  distinct  chambers.  The 
intestine  in  vegetarian  mammals  is  very  long,  being  in  a 
cow  twenty  times  the  length  of  the  body.  In  the  carni- 
vores it  is  comparatively  short — in  a  tiger,  for  example, 
but  two  or  three  times  the  length  of  the  body. 

The  blood  of  mammals  is  warm,  having  a  temperature 
of  from  35°  C.  to  40°  C.  (95°  F.  to  104°  F.).  It  is  red 
in  color,  owing  to  the  reddish-yellow,  circular,  non- 
nucleated  blood-corpuscles.  The  circulation  is  double, 
the  heart  being  composed  of  two  distinct  auricles  and  two 
distinct  ventricles.  Air  is  taken  in  through  the  nostrils 
or  mouth  and  carried  through  the  windpipe  (trachea)  and 
a  pair  of  bronchi  to  the  lungs,  where  it  gives  up  its  oxygen 
to  the  blood,  from  which  it  takes  up  carbonic-acid  gas  in 
turn.  At  the  upper  end  of  the  trachea  is  the  larynx  or 
voice-box,  consisting  of  several  cartilages  attaching  by 
one  end  to  the  vocal  cords  and  by  the  other  to  muscles. 
By  the  alteration  of  the  relative  position  of  these  cartilages 
the  cords  can  be  tightened  or  relaxed,  brought  together 
or  moved  apart,  as  required  to  modulate  the  tone  and 
volume  of  the  voice. 

The  kidneys  of  mammals  are  more  compact  and  definite 
in  form  than  those  of  other  vertebrates.  In  all  mammals 
except  the  Monotremes  they  discharge  their  product 
through  the  paired  ureters  into  a  bladder,  whence  the 
urine  passes  from  the  body  by  a  single  median  urethra. 
Mammary  glands,  secreting  the  milk  by  which  the  young 
are  nourished  during  the  first  period  of  their  existence 
after  birth,  are  present  in  both  sexes  in  all  mr.mmnls, 
though  usually  functional  in  the  female  only. 

The  nervous  system  and  the  organs  of  special  sense 
reach  their  highest  development  in  the  mamnidls.  In 
them  the  brain  is  distinguished  by  its  large  size,  and  by 
the  special  preponderance  of  the  forebrain  or  cerebral 


BRANCH  CHORD  AT  A  :   CLASS  MAMMALIA 


3*5 


fi 


l 


386  ELEMENTARY  ZOOLOGY 

hemispheres  over  the  mid-  and  hind-brain.  Man's  brain 
is  many  times  larger  than  that  of  all  other  known  mam- 
mals of  equal  bulk  of  body,  and  three  times  as  large  as 
that  of  the  largest-brained  ape.  In  man  and  the  higher 
mammals  the  surface  of  the  forebrain  is  thrown  into  many 
convolutions;  among  the  lowest  the  surface  is  smooth. 
Of  the  organs  of  special  sense,  those  of  touch  consist  of 
free  nerve-endings  or  minute  tactile  corpuscles  in  the  skin. 
The  tactile  sense  is  especially  acute  in  certain  regions,  as 
the  lips  and  end  of  the  snout  in  animals  like  hogs,  the 
fingers  in  man,  and  the  under  surface  of  the  tail  in  certain 
monkeys.  All  the  other  sense-organs  are  situated  on  the 
head.  The  organs  of  taste  are  certain  so-called  taste- 
buds  located  in  the  mucous  membrane  covering  certain 
papillae  on  the  surface  of  the  tongue.  The  organ  of 
smell,  absent  only  in  certain  whales,  consists  of  a  ramifi- 
cation of  the  olfactory  nerves  over  a  moist  mucous  mem- 
brane in  the  nose.  The  ears  of  mammals  are  more  highly 
developed  than  those  of  other  vertebrates  both  in  respect 
to  the  greater  complexity  of  the  inner  part  and  the  size 
of  the  outer  part.  A  large  outer  ear  for  collecting  the 
sound-waves  is  present  in  all  but  a  few  mammals.  A 
tympanic  membrane  separates  it  from  the  middle  ear  in 
which  is  a  chain  of  three  tiny  bones  leading  from  the 
tympanum  to  the  inner  ear,  composed  of  the  three  semi- 
circular canals  and  the  spiral  cochlea.  The  eyes  (fig.  150) 
have  the  structure  characteristic  of  the  vertebrate  eye,  con- 
sisting of  a  movable  eyeball  composed  of  parts  through 
which  the  rays  of  light  are  admitted,  regulated,  and  con- 
centrated upon  the  sensitive  expansion,  retina,  of  the  optic 
nerve  lining  the  posterior  part  of  the  ball.  The  eye  is  pro- 
tected by  two  movable  lids.  In  almost  all  mammals  below 
the  Primates  there  is  a  third  lid,  the  nictitating  membrane. 
In  some  burrowing  rodents  and  others  the  eye  is  quite 
vestigial  and  even  concealed  beneath  the  skin 


BRANCH  CHORD  AT  A:   CLASS    MAMMALIA  387 

y.  v 

Development  and  life-history. — All  mammals  except 
the  Monotremes  give  birth  to  free  young.  The  two 
genera  of  Monotremes  produce  their  young  from  eggs 
hatched  outside  the  body;  Tacliyglossus  lays  one  egg 
which  it  carries  in  an  external  pouch,  while  Ornithorhyn- 
''hus  deposits  two  eggs  in  its  burrow.  The  embryo  of 
other  mammals  develops  in  the  lower  portion  of  the  egg- 
lube,  to  the  walls  of  which  it  is  intimately  connected  by 
a  membrane  called  the  placenta.  (In  the  kangaroos  and 
opossums,  Marsupialia,  there  is  no  placenta.)  Through 
this  placenta  blood-vessels  extend  from  the  body  of  the 
mother  to  the  embryo,  the  young  developing  mammal 
thus  deriving  its  nourishment  directly  from  the  parent. 

The  duration  of  gestation  (embryonic  or  prenatal 
development  in  the  mother's  body)  varies  from  three 
weeks  with  the  mouse,  eight  weeks  with  the  cat,  nine 
months  writh  the  stag,  to  t\venty  months  with  the  elephant. 
Like  the  birds,  the  young  of  some  mammals,  the  carni- 
vores for  example,  are  helpless  at  birth,  while  those  of 
others,  as  the  hoofed  mammals,  are  very  soon  able  to  run 
about.  But  all  are  nourished  for  a  longer  or  shorter  time 
by  the  milk  secreted  by  the  mammary  gland  of  the 
mother. 

Habits,  instinct,  and  reason, — Despite  the  wonderful 
examples  of  instinct  and  intelligence  shown  by  many 
insects  and  by  the  other  vertebrates,  especially  the  birds, 
it  is  among  mammals  that  we  find  the  highest  develop- 
ment of  these  qualities  and  of  reason.  In  the  wary  and 
patient  hunting  for  prey  by  the  carnivora,  in  the  gregarious 
and  altruistic  habits  of  the  herding  hoofed  mammals,  in 
the  highly  developed  and  affectionate  care  of  the  young 
shown  by  most  mammals,  and  in  the  loyal  friendship  and 
self-sacrifice  of  dogs  and  horses  in  their  relations  to  man, 
we  see  the  culmination  among  animals  of  the  development 
of  the  functions  of  the  nervous  system.  In  the  character- 


388  ELEMENTARY  ZOOLOGY 

istics  of  intelligence  and  reason  man  of  course  stands 
immensely  superior  to  all  other  animals,  but  both  intelli- 
gence and  reason  are  too  often  shown  by  many  of  the 
other  mammals  not  to  make  us  aware  that  man's  mental 
powers  differ  only  in  degree,  not  in  kind,  from  those  of 
other  animals. 

Pure  instinct  is  hereditary,  and  purely  instinctive  actions 
are  common  to  all  the  individuals  of  a  species.  Those 
actions  which  the  individual  could  not  learn  by  teaching, 
imitation,  or  experience  are  instinctive.  The  accurate 
pecking  at  food  by  chicks  just  hatched  from  an  incubator 
is  purely  instinctive.  Purely  instinctive  also  is  the  laying 
of  eggs  by  a  butterfly  on  a  certain  species  of  plant  which 
may  have  to  be  sought  for  over  wide  acres,  so  that  the 
caterpillars  when  hatched  shall  find  themselves  on  their 
own  special  food-plant.  Yet  the  butterfly  never  ate  of 
this  plant  and  will  never  see  its  young.  Such  elaborate 
instincts  as  these  have  been  developed  from  the  simplest 
manifestations  of  sensation  and  nervous  function,  just  as 
the  complex  structures  of  the  body  have  been  developed 
from  simple  structures  (see  Chapter  XXIX). 

The  feeding  and  domestic  habits  and  the  whole  general 
behavior  of  animals  are  extremely  interesting  subjects  of 
observation  and  study.  And  such  observation  intelli- 
gently pursued  will  be  of  much  value.  The  point  to  be 
kept  ever  in  mind  is  that  all  animal  habits  are  connected 
with  certain  conditions  of  life ;  that  in  every  case  there  is 
an  answer  to  the  question  "why."  This  answer  may 
not  be  found ;  in  many  cases  it  is  extremely  difficult  to 
get  at,  but  often  it  is  simple  and  obvious  and  can  be 
found  by  the  veriest  beginner. 

Classification. — The  mammals  of  North  America  repre- 
sent eight  orders.  Three  additional  mammalian  orders, 
namely,  the  Monotremata,  including  the  extraordinary 
duck-bills  (Ornithorhynchns)  and  a  species  of  Tachyglossus 


BRANCH   CHORD  AT  A:   CLASS  MAMMALIA  389 

in  Australia  and  Tasmania;  the  Edentata,  including  the 
sloths,  armadillos,  and  ant-eaters  found  in  tropical  regions ; 
and  the  Sirenia,  including  the  marine  manatees  and 
dugongs,  are  not  represented  (except  by  a  single  man- 
atee) in  North  America.  In  the  following  paragraphs 
some  of  the  more  familiar  mammals  representing  each  of 
the  eight  orders  represented  in  North  America  are 
referred  to. 

The  opossums  (Marsupialia). — The  opossum  {DiJct- 
phys  Virginia  no)  is  the  only  North  American  representa- 
tive of  the  order  Marsupialia,  the  other  members  of  which 
are  limited  exclusively  to  Australia  and  certain  neighbor- 
ing islands.  The  kangaroos  are  the  best  known  of 
the  foreign  marsupials.  After  birth  the  young  are  trans- 
ferred to  an  external  pouch,  the  marsupium,  on  the 
ventral  surface  of  the  mother,  in  which  they  are  carried 
about  and  fed.  The  opossum  lives  in  trees,  is  about  the 
size  of  a  common  cat,  and  has  a  dirty-yellowish  woolly 
fur.  Its  tail  is  long  and  scaly,  like  a  rat's.  Its  food 
consists  chiefly  of  insects,  although  small  reptiles,  birds, 
and  bird's  eggs  are  eaten.  When  ready  to  bear  young 
the  opossum  makes  a  nest  of  dried  grass  in  the  hollow  of 
a  tree,  and  produces  about  thirteen  very  small  (half  an 
inch  long)  helpless  creatures.  These  are  then  placed  by 
the  mother  in  her  pouch.  Here  they  remain  until  two 
months  or  more  after  birth.  Probably  all  the  North 
American  opossums  found  from  New  York  to  California 
and  especially  common  in  the  Southern  States  belong  to 
a  single  species,  but  there  is  much  variety  among  the 
individuals. 

The  rodents  or  gnawers  (Glires).— The  rabbits,  porcu- 
pines, gophers,  chipmunks,  beavers,  squirrels,  and  rats 
and  mice  compose  the  largest  order  among  the  mammals. 
They  are  called  the  rodents  or  gnawers  (Glires)  because 
of  their  well-known  gnawing  powers  and  proclivities. 


390  ELEMENTARY  ZOOLOGY 

The  special  arrangement  and  character  of  the  teeth  are 
characteristic  of  this  order.  There  are  no  canines,  a 
toothless  space  being  left  between  the  incisors  and  molars 
on  each  side.  There  are  only  two  incisor  teeth  in  each 
jaw  (rarely  four  in  the  upper  jaw),  and  these  teeth  grow 
continuously  and  are  kept  sharp  and  of  uniform  length  by 
the  gnawing  on  hard  substances  and  the  constant  rubbing 
on  each  other.  The  food  of  rodents  is  chiefly  vegetable. 

Of  the  hares  and  rabbits  the  cottontail  (Lepus  mittalii) 
and  the  common  jack-rabbit  (L.  campestris)  are  the  best 
known.  The  cottontail  is  found  all  over  the  United 
States,  but  shows  some  variation  in  the  different  regions. 
There  are  several  species  of  jack-rabbits,  all  limited  to  the 
plains  and  mountain  regions  west  of  the  Mississippi  River. 
The  food  of  rabbits  is  strictly  vegetable,  consisting  of  suc- 
culent roots,  branches,  or  leaves.  Rabbits  are  very 
prolific  and  yearly  rear  from  three  to  six  broods  of  from 
three  to  six  young  each.  There  are  two  North  American 
species  of  porcupines,  an  Eastern  one,  Erethison  dorsatus, 
and  a  Western  one,  E.  epixanthus.  The  quills  in  both 
these  species  are  short,  being  only  an  inch  or  two  in 
length,  and  are  barbed.  In  some  foreign  porcupines  they 
are  a  foot  long.  They  are  loosely  attached  in  the  skin 
and  may  be  readily  pulled  out,  but  they  cannot  be  shot 
out  by  the  porcupine,  as  is  popularly  told.  The  little 
guinea-pigs  (Cavia),  kept  as  pets,  are  South  American 
animals  related  to  the  porcupines. 

The  pocket  gophers,  of  which  there  are  several  species 
mostly  inhabiting  the  central  plains,  are  rodents  found 
only  in  North  America.  They  all  live  underground, 
making  extensive  galleries  and  feeding  chiefly  on  bulbous 
roots.  The  mice  and  rats  constitute  a  large  family  of 
which  the  house-mice  and  rats,  the  various  field-mice,  the 
wood-rat  (Ncotoma  pennsylvanicd)  and  the  muskrat  {Fiber 
zibet  kicus)  are  familiar  representatives.  The  common 


BRANCH   CHORD  AT  A:   CLASS  MAMMALIA  39 J 

brown  rat  (Mus  decumanus)  was  introduced  into  this 
country  from  Europe  about  1775,  and  has  now  nearly 
wholly  supplanted  the  black  rat  (M.  rattus),  also  a 
European  species,  introduced  about  1 544.  The  beaver 
(Castor  canadensis)  is  the  largest  rodent.  It  seems  to  be 
doomed  to  extermination  through  the  relentless  hunting 
of  it  for  its  fur.  The  woodchuck  or  ground-hog  (Arctomys 
monax}  is  another  familiar  rodent  larger  than  most  mem- 
bers of  the  order.  The  chipmunks  and  ground-squirrrels 
are  commonly  known  rodents  found  all  over  the  country. 
They  are  the  terrestrial  members  of  the  squirrel  family, 
the  best  known  arboreal  members  of  which  are  the  red 
squirrel  (Sciurus  hudsonicus),  the  fox-squirrrel  (S.  ludo- 
vicianus),  and  the  gray  or  black  squirrel  (S.  carolinensis). 
The  little  flying  squirrel  (Sciuropterus  volans]  is  abundant 
in  the  Eastern  States. 

The  shrews  and  moles  (Insectivora). — The  shrews 
and  moles  are  all  small  carnivorous  animals,  which, 
because  of  their  size,  confine  their  attacks  chiefly  to  insects. 
The  shrews  are  small  and  mouse -like;  certain  kinds  of 
them  lead  a  semi-aquatic  life.  There  are  nearly  a  score 
of  species  in  North  America.  Of  the  moles,  of  which  there 
are  but  few  species,  the  common  mole  (Scalops  aqitaticui) 
is  well  known,  while  the  star-nosed  mole  (Condylura 
cristatd)  is  recognizable  by  the  peculiar  rosette  of  about 
twenty  cartilaginous  rays  at  the  tip  of  its  snout.  Moles 
live  underground  and  have  the  fore  feet  wide  and  shovel- 
like  for  digging.  The  European  hedgehogs  are  members 
of  this  order. 

The  bats  (Chiroptera).— The  bats  (fig.  153),  order  Chi- 
roptera,  difTer  from  all  other  mammals  in  having  the  fore 
limbs  modified  for  flight  by  the  elongation  of  the  forearms 
and  especially  of  four  of  the  fingers,  all  of  which  are  con- 
nected by  a  thin  leathery  membrane  which  includes  also 
the  hind  feet  and  usually  the  tail.  Bats  are  chiefly  noc- 


392)  ELEMENTARY  ZOOLOGY 

turnal,  hanging-  head  downward  by  their  hind  claws  in 
caves,  hollow  trees,  or  dark  rooms  through  the  day.  They 
feed  chiefly  on  insects,  although  some  foreign  kinds  live 
on  fruits.  There  are  a  dozen  or  more  species  of  bats  in 
North  America,  the  most  abundant  kinds  in  the  Eastern 
States  being  the  little  brown  bat  {Myotis  subulatns),  about 
three  inches  long  with  small  iox-like  face,  high  slender 
ears,  and  a  uniform  dull  olive-brown  color,  and  the  red 
bat  (Lasiurus  borealis),  nearly  four  inches  long,  covered 


FIG.  153. — The  hoary  bat,  Lasitirus  cinereus.     (Photograph  from  life 
by  J.  O.  Snyder.) 

with  long,  silky,  reddish-brown  fur,  mostly  white  at  tips 
of  the  hairs. 

The  dolphins,  porpoises,  and  whales  (Cete). — The 
dolphins,  porpoises,  and  whales  (Cete)  compose  an  order 
of  more  or  less  fish-like  aquatic  mammals,  among  which 


BRANCH   CHORD  AT  A  :   CLASS  MAMMALIA  393 

are  the  largest  of  living  animals.    In  all  the  posterior  limbs 
are  wanting,  and  the  fore   limbs  are  developed  ^s  broad 
flattened  paddles  without  distinct  fingers  or  nails.      The 
tail  ends  in  a  broad  horizontal  fin  or  paddle.      The  Cete 
are  all  predaceous}  fish,  pelagic  crustaceans,  and  especially 
squids  and  cuttlefishes  forming  their  principal  food.     Most 
of  the  species  are  gregarious,  the  individuals  swimming 
together   in    "schools."       The    dolphins    and    porpoises 
compose   a    family    (Delphinidae)    including    the    smaller 
and  many  of  the  most  active  and  voracious  of  the  Cete. 
The    whales    compose    two    families,    the    sperm-whales 
(Physeteridae)    with    numerous    teeth    (in    the   lower    jaw 
only)    and    the    whalebone    whales    (Balaenidae)    without 
teeth,  their  place  being  taken  in  the  upper  jaw  by  an  array 
of  parallel  plates  with  fringed  edges  known  as  "whale- 
bone. ' '      The  great  sperm-whales  or  cachalots  (Pkyseier 
inacrocephalus)  found  in  southern  oceans  reach  a  length 
(males)   of  eighty  feet,  of  which  the  head  forms  nearly 
one-third.     Of  the  whalebone  whales,  the  sulphur-bottom 
(Balcenoptera  sulfured)  of  the  Pacific  Ocean,  reaching  a 
length  of  nearly  one  hundred  feet,  is  the  largest,  and  hence 
the    largest   of  all   living  animals.      The  common    large 
whale  of  the  Eastern  coast  and  North  Atlantic  is  the  right 
whale   (Bal&na  glacialis] ;    a   near   relative  is   the   great 
bowhead   (B.    mysticetus)   of  the   Arctic   seas,   the   most 
valuable  of  all  whales  -to  man.      Whales  are  hunted  for 
their  whalebone  and  the  oil  yielded  by  their  fat  or  blubber. 
The    story  of  whale-fishing  is   an   extremely  interesting 
one,  the  great  size  and  strength  of  the  "game  "  making 
the  ' '  fishing  ' '  a  hazardous  business. 

The  hoofed  mammals  (Ungulata). — The  order  Ungu- 
lata  includes  some  of  the  most  familiar  mammal  forms. 
Most  of  the  domestic  animals,  as  the  horse,  cow,  hog, 
sheep,  and  goat,  belong  to  this  order,  as  well  as  the 
familiar  deer,  antelope,  and  buffalo  of  our  own  land  and 


394  ELEMENTARY  ZOOLOGY 

the  elephant,  rhinoceros,  hippopotamus,  giraffe,  camel, 
zebra,  etc.,  familiar  in  zoological  gardens  and  menageries. 
The  order  is  a  large  one,  its  members  being  characterized 
by  the  presence  of  from  one  to  four  hooves,  which  are  the 
enlarged  and  thickened  claws  of  the  toes.  The  Ungulates 
are  all  herbivorous,  and  have  their  molar  teeth  fitted  for 


FIG.  154. — Male  elk  or  wapiti,  Cervus  canadensis.  (Photograph  by  E. 
Willis  from  specimen  mounted  by  Prof.  L.  L.  Dyche,  University  of 
Kansas.) 

grinding,  the  canines  being  absent  or  small.  The  order 
is  divided  into  the  Perissodactyla  or  odd-toed  forms,  like 
the  horse,  zebra,  tapir,  and  rhinocerus,  and  the  Artio- 
dactyla  or  even-toed  forms,  like  the  oxen,  sheep,  deer, 


BRANCH  CHORD  AT  A:   CLASS  MAMMALIA 


395 


camels,  pigs,  and  hippopotami.  •  The  Artiodactyls  com- 
prise two  groups,  the  Ruminants  and  Non-ruminants. 
All  of  the  native  Ungulata  of  our  Northern  States  belong 
to  the  Ruminants,  so  called  because  of  their  habit  of 


chewing  a  cud.  A  ruminant  first  presses  its  food  into  a 
ball,  swallows  it  into  a  particular  one  of  the  divisions  of 
its  four-chambered  stomach,  and  later  regurgitates  it  into 


$96  ELEMENTARY  ZOOLOGY 

the  mouth,  thoroughly  masticates  it,  and  swallows  it 
again,  but  into  another  stomach-chamber.  From  this  it 
passes  through  the  other  two  into  the  intestine. 

The  deer  family  (Cervidae)  comprises  the  familiar  Vir- 
ginia or  red  deer  (Odoccileus  americamis)  of  the  Eastern 
and  Central  States  and  the  white-tailed,  black-tailed,  and 
mule  deers  of  the  West,  the  great-antlered  elk  or  wapiti 
(Ccrvtis  canadensis)  (fig.  154),  the  great  moose  (Alee 
amcricand]  (fig.  152),  largest  of  the  deer  family,  and  the 
American  reindeer  or  caribou  (Rangifcr  caribou}.  All 
species  of  the  Cervidae  have  solid  horns,  more  or  less 
branched,  which  are  shed  annually.  Only  the  males  (ex- 
cept with  the  reindeer)  have  horns.  The  antelope  (Anti- 
locapra  amcricana)  (fig.  155)  common  on  the  Western 
plains  also  sheds  its  horns,  which,  however,  are  not  solid 
and  do  not  break  off  at  the  base  as  in  the  deer,  but  are 
composed  of  an  inner  bony  core  and  an  outer  horny 
sheath,  the  outer  sheath  only  being  shed.  The  family 
Bovidae  includes  the  once  abundant  buffalo  or  bison  (Bison 
bison)  (frontispiece),  the  big-horn  or  Rocky  Mountain 
sheep  (Ovis  canadensis]  (fig.  151),  and  the  strange  pure- 
white  Rocky  Mountain  goat  (Oreamnos  montanus}.  The 
buffalo  was  once  abundant  on  the  Western  plains,  travelling 
in  enormous  herds.  But  so  relentlessly  has  this  fine  animal 
been  hunted  for  its  skin  and  flesh  that  it  is  now  practically 
exterminated  (fig.  156).  A  small  herd  is  still  to  be  found 
in  Yellowstone  Park,  and  a  few  individuals  live  in  parks 
and  zoological  gardens.  In  all  of  the  Bovidae  the  horns 
are  simple,  hollow,  and  permanent,  each  enclosing  a 
bony  core. 

The  carnivorous  mammals  (Ferae). — The  order  Ferae 
includes  all  those  mammals  usually  called  the  carnivora, 
such  as  the  lions,  tigers,  cats,  wolves,  dogs,  bears, 
panthers,  foxes,  weasels,  seals,  etc.  All  of  them  feed 
chiefly  on  animal  substance  and  are  predatory,  pursuing 


BRANCH  CHORD  AT  A:   CLASS  MAMMALIA 


397 


and  killing  their  prey.  They  are  mostly  fur-covered  and 
many  are  hunted  for  their  skin.  They  have  never  less 
than  four  toes,  which  are  provided  with  strong  claws  that 
are  frequently  more  or  less  retractile.  The  canine  teeth 
are  usually  large,  curved,  and  pointed. 

While  most  of  the  Ferae  live  on  land,  some  are  strictly 
aquatic.  The  true  seals,  fur-seals,  sea-lions,  and  walruses 
comprise  the  aquatic  forms,  all  being  inhabitants  of  the 
ocean.  The  true  seals,  of  which  the  common  harbor  seal 
(Phoca  I'itulina)  is  our  most  familiar  representative,  have 


FIG.  156. — A  buffalo,  Bison  bison,  killed  for  its  skin  and  tongue,  on  the 
plains  of  Western  Kansas  thirty  years  ago.  (Photograph  by  J.  Lee 
Knight.) 

the  limbs  so  thoroughly  modified  for  swimming  that  they 
are  useless  on  land.  The  fur-seals,  sea-lions,  and  walruses 
use  the  hind  legs  to  scramble  about  on  the  rocks  or 


39^  ELEMENTARY  ZOOLOGY 

beaches  of  the  shore.  The  fur-seals  (fig.  157)  live  gre- 
gariously in  great  rookeries  on  the  Pribilof  or  Fur  Seal 
Islands,  and  the  Commander  Islands  in  Bering  Sea. 

The  bears  are  represented  in  our  country  by  the  wide- 
spread brown,  black,  or  cinnamon  bear  (Ursus  americanus) 
and  the  huge  grizzly  bear  (U.  horribilis]  of  the  West.  The 
great  polar  bear  (Thalarctos  maritinms)  lives  in  arctic 
regions.  The  otters,  skunks,  badgers,  wolverines,  sables, 
minks,  and  weasels  compose  the  family  Mustelidae,  which 
includes  most  of  the  valuable  fur-bearing  animals.  Some 
of  the  members  of  this  family  lead  a  semi-aquatic  or  even 
strictly  aquatic  life  and  have  webbed  feet.  The  wolves, 
foxes,  and  dogs  belong  to  the  family  Canidae.  The  coyote 
(Cam's  latrans],  the  gray  wolf  (C.  nubilus),  and  the  red 
fox  ( Vulpes  pennsylvanicus)  are  the  most  familiar  repre- 
sentatives of  this  family,  in  addition  to  the  dog  (C.  fami- 
liar is),  which  is  closely  allied  to  the  wolf.  "Most 
carnivorous  of  the  carnivora,  formed  to  devour,  with  every 
offensive  weapon  specialized  to  its  utmost,  the  Felidae, 
\vhether  large  or  small,  are,  relatively  to  their  size,  the 
fiercest,  strongest,  and  most  terrible  of  beasts."  The 
Felidae  or  cat  family  includes  the  lions,  tigers,  hyenas, 
leopards,  jaguars,  panthers,  wildcats,  and  lynxes.  In  this 
country  the  most  formidable  of  the  Felidae  is  the  American 
panther  or  puma  (Felts  concolor).  It  reaches  a  length 
from  nose  to  root  of  tail  of  over  four  feet.  Its  tail  is 
long.  The  wildcat  (Lynx  riifus)  is  much  smaller  and 
has  a  short  tail. 

The  man-like  mammals  (Primates). — The  Primates, 
the  highest  order  of  mammals,  includes  the  lemurs, 
monkeys,  baboons,  ape-s,  and  men.  Man  {Homo  sapiens] 
is  the  only  native  representative  of  this  order  in  our 
country.  All  the  races  and  kinds  of  men  known,  although 
really  showing  much  variety  in  appearance  and  body 
structure,  are  commonly  included  in  one  species.  The 


BRANCH  CHORDATA:   CLASS  MAMMALIA  399 


*:  S 
'*  § 


. 


400 


ELEMENTARY  ZOOLOGY 


chief  structural  characteristics  which  distinguish  man  from 
the  other  members  of  this  order  are  the  great  development 
of  his  brain  and  the  non-opposability  of  his  great  toe. 
Despite  the  similarity  in  general  structure  between  him 


FIG.  158. — "  Bob  Jordan,"  a  monkey  of  the  genus  Cercopit/iecus. 
(Photograph  from  life  by  D.  S.  Jordan.) 

and  the  anthropoid  apes  of  the  Old  World,  in  particular 
the  chimpanzee  and  orang-outang,  the  disparity  in  size  of 
brain  is  enormous. 

The  lowest  Primates  are  the  lemurs  found  in  Madagas- 
car, in  which  island  they  include  about  one-half  of  all 
the  mammalian  species  found  there.  The  brain  is  much 


BRANCH   CHORD  AT  A  :   CLASS  MAMMALIA  401 

less  developed  in  the  lemurs  than  in  any  of  the  other 
monkeys.  The  monkeys  and  apes  may  be  divided  into 
two  groups,  the  lower,  platyrrhine  monkeys,  found  in  the 
New  World,  and  the  higher,  catarrhine  forms,  limited  to 
the  Old  World.  The  platyrrhine  monkeys  have  wide  noses 
in  which  the  nostrils  are  separated  by  a  broad  septum  and 
with  the  openings  directed  laterally.  These  monkeys  are 
mostly  smaller  and  weaker  than  the  Old  World  forms  and 
are  always  long-tailed,  the  tail  being  frequently  prehen- 
sile. They  include  the  howling,  squirrel,  spider,  and 
capuchin  monkeys  common  in  the  forests  of  tropical  South 
America.  The  catarrhine  monkeys  have  the  nose-septum 
narrow  and  the  openings  of  the  nostrils  directed  forwards, 
and  the  tail  is  wanting  in  numerous  members  of  the  group. 
They  include  the  baboons,  gorillas,  orang-outangs,  and 
chimpanzees.  These  apes  have  a  dentition  approaching 
that  of  man,  and  in  all  ways  are  the  animals  which  most 
nearly  resemble  man  in  physical  character. 


PART  III 

ANIMAL  ECOLOGY 

CHAPTER  XXIX 

THE    STRUGGLE    FOR    EXISTENCE,    ADAPTA- 
TION,   AND    SPECIES-FORMING 

TECHNICAL  NOTE. —  Multiplication,  or  increase  by  geometric 
ratio,  among  animals  can  be  illustrated  by  noting  the  many  eggs 
laid  by  a  single  female  moth  or  beetle  or  fly  or  mosquito  or  any 
other  common  insect  (or  almost  any  other  non-mammalian  animal). 
The  production  of  many  live  young  by  each  female  rose  aphid  can 
be  readily  seen  ;  the  number  of  young  in  a  litter  of  kittens  or  pups 
or  rabbits  is  a  good  illustration.  From  this  geometric  increase  it  is 
obvious  that  there  must  be  a  great  crowding  of  animals  and  a  strug- 
gle among  them  for  existence.  This  struggle  and  the  downfall  of 
the  many  and  success  of  the  victorious  few  can  be  observed  by 
rearing  in  a  small  jar  of  water  all  the  young  of  a  single  brood  of 
water-tigers  (larva  of  Dyticus}  or  other  aquatic  predaceous  insect. 
The  strongest  young  will  live  by  killing  and  eating  the  weaker  of 
their  own  kind.  In  a  spider's  egg-sac  the  young  after  hatching  do 
not  immediately  leave  the  sac,  but  remain  in  it  for  several  days. 
During  this  time  they  live  on  each  other,  the  strongest  feeding  on 
the  weaker.  Thus  out  of  many  spiderlings  hatched  in  each  sac  com- 
paratively few  issue.  This  can  be  readily  observed.  Open  several 
egg-sacs  and  count  the  eggs  in  them.  Let  the  spiderlings  hatch 
and  issue  from  some  other  egg-sacs  belonging  to  the  same  species 
of  spider.  The  number  of  issuing  spiderlings  will  always  be  much 
less  than  that  of  the  eggs.  The  actual  working  of  natural  selection 
and  the  forming  of  new  species  can  of  course  be  seen  only  in  re- 
sults, and  not  in  process.  The  great  variety  of  adaptation,  the  fit- 
ness of  adaptive  structures,  can  be  readily  illustrated  among  the 
commonest  animals.  Animals  showing  certain  striking  and  unusual 
adaptations  will  perhaps  make  the  matter  more  obvious.  To  all 
teachers  will  occur  numerous  opportunities  of  illustrating,  by  refer- 

403 


404  ELEMENTARY  ZOOLOGY 

ence  to  actual  processes  or  to  obvious  results,  the  principles  of  this 
chapter. 

The  multiplication  and  crowding  of  animals. — In  the 

reproduction  or  multiplication  of  animals  the  production 
of  young  proceeds  in  geometric  ratio,  that  is,  it  is  truly  a 
multiplication.  Any  species  of  animal,  if  its  multiplica- 
tion proceeded  unchecked,  would  sooner  or  later  be 
sufficiently  numerous  to  populate  exclusively  the  whole 
world.  The  elephant  is  reckoned  the  slowest  breeder  of 
all  known  animals.  It  begins  breeding  when  thirty  years 
old  and  goes  on  breeding  until  ninety  years  old,  bringing 
forth  six  young  in  the  interval,  and  surviving  until  a 
hundred  years  old.  Thus  after  about  eight  hundred  years 
there  would  be,  if  all  the  individuals  lived  to  their  normal 
age  limit,  19,000,000  elephants  alive  descended  from  the 
first  pair.  A  few  years  more  of  unchecked  multiplication 
of  the  elephant  and  every  foot  of  land  on  the  earth  would 
be  covered  by  them.  But  the  rate  of  multiplication  of 
other  animals  varies  from  a  little  to  very  much  greater 
than  that  of  the  elephant.  It  has  been  shown  that  at  the 
normal  rate  in  increase  in  English  sparrows,  if  none  were 
to  die  save  of  old  age,  it  would  take  but  twenty  years  to 
give  one  sparrow  to  every  square  inch  in  the  State  of 
Indiana.  The  rate  of  increase  of  an  animal,  each  pair 
producing  ten  pairs  annually  and  each  animal  living  ten 
years,  is  shown  in  the  following  table: 

Years.        Pairs  produced.  Pairs  alive  at  end  of  year. 

1  10  II 

2  110  121 

3  1,210  1,331 

4  i3>3!0  14,641 

5  146,410  161,051 
10                                                       25,937,424,600 

20  700,000,000,000,000,000,000 


THE  STRUGGLE  FOR  EXISTENCE  405 

Some  animals  produce  vast  numbers  of  eggs  or  young; 
for  example,  the  herring,  20,000;  a  certain  eel,  several 
millions;  and  the  oyster  from  500,000  to  16,000,000. 
Supposing  we  start  with  one  oyster  and  let  it  produce  one 
million  of  eggs.  Let  each  egg  produce  an  oyster  which 
in  turn  produces  *  one  million  of  eggs,  and  let  these  go 
on  increasing  at  the  same  rate.  In  the  second  generation 
there  would  be  one  million  million  of  oysters,  and  in  the 
fourth,  i.e.  the  great  great  grandchildren  of  the  first  oyster, 
there  would  be  one  million  million  million  million  of 
oysters.  The  shells  of  these  oysters  would  just  about 
make  a  mass  the  size  of  the  earth. 

But  it  is  obvious  that  all  the  new  individuals  of  any 
animal  produced  do  not  live  their  normal  duration  of  life. 
All  animals  produce  far  more  young  than  can  survive. 
As  a  matter  of  fact,  which  we  may  verify  by  observation, 
the  number  of  individuals  of  animals  in  a  state  of  nature  is, 
in  general,  about  stationary.  There  are  about  as  many 
squirrels  in  the  forest  one  year  as  another,  about  as  many 
butterflies  in  the  field,  about  as  many  frogs  in  the  pond. 
Some  species  increase  in  numbers,  as  for  example,  the 
rabbit  in  Australia,  which  was  introduced  there  in  1860 
and  in  fifteen  years  had  become  so  abundant  as  to  be  a 
great  pest.  Other  species  decrease,  as  the  buffaloes,  which 
once  roamed  our  great  plains  in  enormous  herds  and  are 
now  represented  by  a  total  of  a  few  hundred  individuals, 
and  the  passenger-pigeon,  whose  migrating  flocks  ten  years 
ago  darkened  the  air  for  hours  in  parts  of  the  Mississippi 
valley,  where  now  it  is  a  rare  bird.  But  the  hand  of  man 
is  the  agent  which  has  helped  to  increase  or  to  check  the 
multiplication  of  these  animals.  In  nature  such  quick 
changes  rarely  occur. 


*  Oysters  are  hermaphroditic,  each  individual  producing  both  sperm-  and 
egg-cells. 


406  ELEMENTARY  ZOOLOGY 

The  struggle  for  existence. — The  numbers  of  animals 
are  stationary  because  of  the  tremendous  mortality  occa- 
sioned by  the  constant  preying  on  eggs  and  young  and 
adults  by  other  animals,  because  of  strenuous  and  destruc- 
tive climatic  and  meteorological  conditions,  and  because 
there  is  not  space  and  food  for  all  born,  not  even,  indeed, 
for  all  of  a  single  species,  let  alone  all  of  the  hundreds  of 
thousands  of  species  which  now  inhabit  the  earth.  There 
is  thus  constantly  going  on  among  animals  a  fearful 
struggle  for  existence.  In  the  case  of  any  individual  this 
struggle  is  threefold:  (i)  with  the  other  individuals  of  his 
own  species  for  food  and  space;  (2)  with  the  individuals 
of  other  species,  which  prey  on  him,  or  serve  as  his  prey, 
or  for  food  and  space;  and  (3)  finally  with  the  conditions 
of  life,  as  with  the  cold  of  winter,  the  heat  of  summer,  or 
drouth 'and  flood.  Sometimes  one  of  these  struggles  is 
the  severer,  sometimes  another.  With  the  communal 
animals  the  struggle  among  individuals  is  lessened — they 
help  each  other ;  but  when  the  struggle  with  the  condi- 
tions of  life  are  easiest,  as  in  the  tropics  or  in  the  ocean, 
the  struggle  among  individuals  becomes  intensified.  Each 
strives  to  feed  itself,  to  save  its  own  life,  to  produce  and 
safeguard  its  young.  But  in  spite  of  all  their  efforts  only 
a  few  individuals  out  of  the  hosts  produced  live  to 
maturity.  The  great  majority  are  destroyed  in  the  egg 
or  in  adolescence. 

Variation  and  natural  selection. — What  individuals 
survive  of  the  many  which  are  born  ?  Those  best  fitted 
for  life;  those  which  are  a  little  stronger,  a  little  swifter, 
a  little  hardier,  a  little  less  readily  preceived  by  their 
enemies,  than  the  others.  They  are  the  winners  in  the 
struggle  for  existence;  they  are  the  survivors.  And  this 
survival  of  the  fittest,  as  it  is  called,  is  practically  a  process 
of  selection  by  Nature.  Nature  selects  the  fittest  to  live 
and  to  perpetuate  the  species.  Their  progeny  again 


THE  STRUGGLE  FOR  EXISTENCE  407 

undergo  the  struggle  and  the  selecting  process,  and  again 
the  fittest  live.  And  so  on  until  adjustment  or  harmoniz- 
ing of  animals'  bodies  and  habits  with  the  conditions  of 
life,  with  their  environment,  comes  to  be  extremely  fine 
and  nearly  perfect. 

It  is  evident,  of  course,  that  such  a  natural  selection  or 
survival  of  the  fittest  and  consequent  adaptation  to  en- 
vironment presupposes  differences  among  the  individuals 
of  a  species.  And  this  is  an  observed  fact.  No  two 
individuals,  although  of  the  same  brood,  are  exactly  alike 
at  birth ;  there  always  exist  slight  variations  in  structure 
and  performance  of  functions.  And  these  slight  variations 
are  the  differences  which  determine  the  fate  of  the  indi- 
vidual. One  individual  is  a  little  larger  or  stronger  or 
swifter  or  hardier  than  its  mates.  The  existence  of  this 
variation  we  know  from  our  observation  of  the  young 
kittens  or  puppies  of  a  brood.  So  it  is  with  all  animals. 
Thus  natural  selection  depends  upon  two  factors,  namely, 
the  excess  in  the  production  of  new  individuals  and  the 
consequent  struggle  for  existence  among  them,  and  the 
existence  of  variations  which  give  certain  individuals 
slight  advantages  in  this  struggle. 

Adaptation  and  adjustment  to  surroundings. — The 
action  of  natural  selection  obviously  must,  and  does, 
result  in  a  fine  adaptation  and  adjustment  of  the  structure 
and  habits  of  animals  to  their  surroundings.  If  a  certain 
species  or  group  of  individuals  cannot  adapt  itself  to  its 
environment,  it  will  be  crowded  out  by  others  that  can. 
A  slight  advantageous  variation  comes  in  time  by  the 
continuously  selective  process  to  be  a  well-developed 
adaptation. 

The  diverse  forms  and  habits  possessed  by  animals  are 
chiefly  adaptations  to  their  special  conditions  of  life. 
The  talons  and  beak  of  the  eagle,  the  fishing-pouch  of  the 
pelican,  the  piercing  chisel-like  bill  of  the  woodpecker, 


4o8  ELEMENTARY  ZOOLOGY 

and  the  sensitive  probing-bill  of  the  snipe  are  adaptations 
connected  with  the  special  feeding  habits  of  these  birds. 
The  quills  of  the  porcupine,  the  poison-fangs  of  the  rattle- 
snake, the  sting  of  the  yellow-jacket,  and  the  antlers  of 
the  deer  are  adaptations  for  self-defence.  The  fins  and 
gills  of  fishes,  the  shovel-like  fore  feet  of  the  mole,  the 
wings  of  birds  and  insects  and  bats,  the  toe-pads  of  the 
tree-toad,  the  leaping-legs  of  the  grasshopper,  all  these 
are  adaptations  concerned  with  the  special  life-surround- 
ings of  these  animals. 

Adaptations  may  relate  to  habits  and  behavior  as  well 
as  to  structure.  Plainly  adaptive  are  such  habits  as  the 
migration  of  birds  and  some  other  animals,  most  of  the 
habits  connected  with  food-getting,  and  especially  striking 
and  interesting  those  connected  with  the  production  and 
care  of  the  young,  including  nest-making  and  home- 
building. 

Species-forming. — It  is  evident  that  through  the  cumu- 
lative action  of  natural  selection,  animals  of  a  structural 
type  considerably  (even  unlimitedly)  different  from  any 
original  type  may  in  time  be  produced  by  the  gradual 
modification  of  the  original  type  under  new  conditions. 
If,  for  example,  a  few  individuals  of  a  mainland  species 
should  come  to  be  thrown  as  waifs  of  wave  and  storm 
upon  an  island,  and  if  these  should  be  able  to  maintain 
themselves  there  and  produce  young,  increasing  so  as  to 
occupy  the  new  territory,  there  would  be  produced  in  time 
a  new  type  of  individual  conforming  or  adapted  to  the 
conditions  obtaining  in  the  island,  these  conditions  being, 
of  course,  almost  certainly  different  from  those  of  the 
mainland.  Thus  as  an  offshoot  or  derivation  from  the 
original  type  still  existing  on  the  mainland  we  should 
have  the  new  island-inhabiting  type.  Now  when  these 
island  individuals  come  to  differ  so  much,  structurally  and 
physiologically,  from  the  mainland  type  that  they  cannot, 


THE  STRUGGLE  FOR  EXISTENCE  400 

even  if  opportunity  offers,  successfully  mate  or  interbreed 
with  mainland  individuals  the  island  type^constitutes  a 
new  species.  That  is,  our  distinction  between  species 
rests  not  only  on  structural  differences,  but  on  the  impossi- 
bility of  interbreeding  (at  least  for  the  production  of  fertile 
young).  Such  a  combination  of  the  action  of  natural 
selection  and  the  condition  of  isolation  (as  illustrated  by 
the  case  of  island  animals),  is  probably  the  most  potent 
factor  in  the  production  of  new  species  of  animals  (and 
plants). 

For  accounts  of  the  struggle-  for  existence,  variations, 
adaptations,  natural  selection  and  species-forming  see 
Darwin's  "Origin  of  Species,"  Wallace's  *'  Island  Life," 
and  Romanes'  "  Darwin  and  After  Darwin,"  I. 

Artificial  selection. — When  a  selection  among  the 
individuals  of  a  species,  that  is,  the  choosing  and  preserv- 
ing of  individuals  which  show  a  certain  trait  or  traits  and 
the  destroying  of  those  individuals  not  possessing  this 
trait,  is  done  by  man,  it  is  called  artificial  selection.  To 
artificial  selection  we  chiefly  owe  all  the  many  races  or 
varieties  of  our  domesticated  animals  and  plants.  For 
example,  from  the  ancestral  jungle  fowl  have  been  devel- 
oped by  artificial  selection  (and  by  cross-breeding)  all  our 
kinds  of  domestic  fowl,  as  Brahmas,  black  Spanish, 
bantams,  game-cocks,  etc.  ;  from  the  wild  rock-dove  have 
been  developed  our  various  fancy  pigeons,  as  carriers, 
pouters,  fan  tails,  etc. 

For  an  account  of  artificial  selection  see  Darwin's 
"Plants  and  Animals  under  Domestication,"  and 
Romanes'  "  Darwin  and  After  Darwin,"  I. 


CHAPTER   XXX 

SOCIAL     AND     COMMUNAL     LIFE,      COMMEN- 
SALISM    AND    PARASITISM 

Social  life  and  gregariousness. — TECHNICAL    NOTE.— 

Students  should  refer  to  examples  of  gregariousness  from  their  own 
observations  of  animals.  The  roosting  together  of  crows  and  of  black- 
birds ;  the  gathering  of  swallows  preparatory  to  migration  ;  the 
flocking  of  geese  and  ducks,  with  leaders,  in  their  migratory  flights, 
all  can  be  readily  observed.  From  observation  or  general  reading 
students  will  be  more  or  less  familiar  with  prairie-dog  villages, 
beaver-dams  and  marshes,  the  one-time  great  herds  of  bison,  etc. 

The  struggle  for  existence  is  always  operative ;  but  in 
some  cases  one  or  more  phases  of  it  may  be  ameliorated. 
For  example,  the  amelioration  of  the  struggle  among 
individuals  of  one  species  obtains  in  a  lesser  or  greater 
degree  in  the  case  of  those  animals  which  exhibit  a  social 
life,  of  which  mutual  aid  and  mutual  dependence  are  the 
basis.  The  honey-bee  and  the  ants  are  familiar  examples 
of  animals  which  show  a  high  degree  of  social  life.  They 
live,  indeed,  a  truly  communal  life,  where  the  fate  of  the 
individual  is  bound  up  in  the  fate  of  the  community. 
But  there  are  many  animals  which  show  a  much  lower 
degree  of  mutual  aid  and  a  far  less  coherent  society. 
The  simplest  form  of  social  life  exists  among  those  animals 
in  which  many  individuals  of  one  species  keep  together, 
forming  a  great  band  or  herd.  In  this  case  there  is  not 
nearly  so  much  mutual  aid  or  mutual  dependence  as  in 
that  of  the  honey-bee,  and  the  safety  of  the  individual  is 
\ot  wholly  bound  up  in  the  fate  of  the  herd.  Such 

410 


SOCIAL   AND  COMMUNAL   LIFE  41 1 

animals  are  said  to  be  gregarious  in  habit,  and  this  gre- 
gariousness  is  undoubtedly  advantageous  to  the  individuals 
of  the  band.  The  great  herds  of  reindeer  in  the  North, 
and  of  the  bison  or  buffalo  which  once  ranged  over  the 
Western  American  plains  are  examples  of  a  gregarious- 
ness  in  which  mutual  protection  from  enemies,  like  wolves, 
seems  to  be  the  principal  advantage  gained.  The  bands 
of  wolves  which  hunted  the  buffalo  show  the  advantage 
of  mutual  help  in  aggression  as  well  as  in  protection. 
Prairie-dogs  live  in  great  villages  or  communities  which 
spread  over  many  acres.  By  shrill  cries  they  tell  each 
other  of  the  approach  of  enemies,  and  they  seem  to  visit 
each  other  and  to  enjoy  each  other's  society  a  great  deal, 
although  that  they  are  thus  afforded  much  actual  active 
help  is  not  apparent.  The  beavers  furnish  a  well-known 
and  very  interesting  example  of  mutual  help ;  they  exhibit 
a  communal  life  although  a  simple  one.  They  live  in 
villages  or  communities,  all  helping  to  build  the  dam 
across  the  stream  which  is  necessary  to  form  the  marsh 
or  pool  in  which  the  nests  or  houses  are  built. 

Communal  life. — TECHNICAL  NOTE. — See  technical  notes, 
pp.  212  et  seq,  for  directions  for  work  in  connection  with  the  study 
of  the  communal  life  of  ants,  bees,  and  wasps. 

When  many  individuals  of  a  species  live  together  in  a 
community  in  which  the  different  kinds  of  work  are  divided 
more  or  less  distinctly  among  the  different  members  and 
where  each  individual  works  primarily  for  the  whole  and 
•  not  for  himself;  where  there  is,  in  other  words,  a  thorough 
mutual  help  and  mutual  dependence  among  the  members 
of  the  community  accompanied  by  a  division  of  labor,  the 
life  of  the  species  is  truly  communal.  Those  animals 
which  show  the  most  elaborate  and  specialized  communal 
life  are  the  termites  or  white  ants,  the  social  bees  and 
wasps,  and  the  true  ants.  Of  these  the  ants  and  honey- 


4i2  ELEMENTARY  ZOOLOGY 

bees  stand  first.  As  already  explained  (see  pp.  22O  et  seq), 
there  are  among  these  communal  insects  several  different 
kinds  of  individuals  in  each  species.  With  most  animals 
there  are  two  kinds  only,  males  and  females,  which  may 
or  may  not  show  differences  in  color,  form,  etc.,  so  that 
they  are  readily  distinguishable.  Among  all  the  com- 
munal insects,  however,  there  are  always  three  kinds  of 
individuals,  males,  females,  and  workers,  these  last  being 
infertile  individuals.  With  the  social  wasps  and  social 
bees  the  workers  are  all  infertile  females  and  are  smaller 
than  the  fertile  forms;  with  the  termites  there  are 
besides  the  fertile  males  and  females,  which  are  winged, 
workers  which  are  wingless,  and  also  peculiar  wingless 
individuals  called  soldiers  which  have  very  large  jaws  and 
whose  business  it  is  to  fight  off  attacking  enemies  of 
the  community.  Among  the  ants  the  workers  are  also 
wingless,  while  the  males  and  females  are  winged.  The 
worker  ants  in  many  species  are  of  two  kinds,  so»called 
worker  majors  and  worker  minors,  differing  markedly  in 
size.  All  the  ant  workers  are  good  soldiers,  but  with 
some  the  fighting  is  done  almost  wholly  by  certain 
especially  large-headed  and  large-jawed  ones  which  may 
be  called  soldier-workers. 

Thus  among  all  strictly  communal  animals  there  is  a 
specialization  or  differentiation  of  individuals  accompany- 
ing the  division  of  labor.  Special  individuals  have  a 
certain  part  of  the  work  of  the  community  to  do,  and  they 
are  specially  modified  in  structure  to  do  this  work.  This 
structural  modification  may  make  them  incapable  of  per- 
forming certain  other  labor  or  work  wrhich  is  necessary 
for  their  living  and  which  must  be  done  for  them,  therefore, 
by  others.  Thus  the  mutual  interdependence  of  the  in- 
dividuals composing  a  colony  is  very  real.  The  worker 
honey-bees  cannot  perpetuate  the  species;  honey-bees 
would  die  out  were  it  not  for  the  males  and  females.  But 


SOCIAL  AND  COMMUNAL  LIFE  4*3 

the  males  and  females  have  given  up  the  functions  of  food- 
getting  and  of  caring  for  their  young ;  did  not  the  workers 
do  these  things  for  them,  the  community  would  die  out 
quite  as  soon. 

The  advantages  of  communal  or  social  life,  of  co-opera- 
tion and  mutual  aid  are  real.  Those  animals  that  have 
adopted  such  a  life  are  among  the  most  successful  of  all 
in  the  struggle  for  existence.  The  termite  worker  is 
one  of  the  most  defenseless  and  for  those  animals  that 
prey  on  insects  one  of  the  most  toothsome  insects,  and 
yet  the  termite  is  one  of  the  most  abundant  and  success- 
fully living  insect  kinds  in  all  the  tropics.  Ants  are 
everywhere  and  are  everywhere  successful.  The  honey- 
bee is  a  popular  type  of  successful  life.  The  artificial 
protection  afforded  it  by  man  may  aid  it  in  its  struggle 
for  existence,  but  it  gains  this  protection  because  of  certain 
features  of  its  communal  life,  and  in  nature  the  honey-bee 
takes  care  of  itself  well.  Co-operation  and  mutual  aid 
are  among  the  most  important  factors  which  help  in  the 
struggle  for  existence. 

Commensalism. — TECHNICAL  NOTE. — Examine  ants'  nests 
to  find  myrmecophilous  insects.  If  on  the  seashore  search  for  hermit- 
crabs  with  sea-anemones  on  shell.  If  inland,  try  to  have  some  pre- 
served specimens  showing  the  crabs  and  sea-anemones. 

The  phases  of  living  together  and  mutual  help  just  dis- 
cussed concerned  in  each  instance  a  single  species  of 
animal.  All  the  members  of  a  pack  of  wolves  or  of  a 
honey-bee  community  belong  to  a  single  species.  But 
there  are  numerous  instances  known  of  the  mutually 
advantageous  association  of  individuals  of  two  different 
species.  Such  an  association  is  called  commensalism  or 
symbiosis. 

The  hermit-crabs  live,  as  has  been  learned  (p.  154),  in 
the  shells  of  molluscs,  most  of  the  body  of  the  crab  being 
concealed  within  the  shell,  only  the  head  and  the  grasping 


414  ELEMENTARY  ZOOLOGY 

and  walking  legs  protruding.  In  some  species  of  hermit- 
crabs  there  is  always  to  be  found  on  the  shell  near  the 
opening  a  sea-anemone.  "This  sea-anemone  is  carried 
from  place  to  place  by  the  crab,  and  in  this  way  is  much 
aided  in  obtaining  food.  On  the  other  hand,  the  crab  is 
protected  from  its  enemies  by  the  well-armed  and  dan- 
gerous tentacles  of  its  companion.  On  the  tentacles  there 
are  many  thousand  long  slender  stinging  threads,  and  the 
fish  that  would  eat  the  hermit-crab  must  first  deal  with 
the  stinging  anemone."  If  the  sea-anemone  be  torn 
away  from  the  shell  the  crab  will  wander  about  seeking 
another  anemone.  When  he  finds  one,  he  struggles  to 
loosen  it  from  the  rock  to  which  it  is  attached,  and  does 
not  rest  until  he  has  torn  it  loose  and  placed  it  on  his 
shell. 

In  the  case  of  the  hermit-crab  and  the  sea-anemone 
there  is  no  doubt  of  the  mutual  advantage  derived  from 
their  communal  life.  But  this  mutual  advantage  is  not 
so  obvious  in  some  cases  of  commensalism,  where  indeed 
most  or  all  of  the  advantage  often  seems  to  lie  with  one 
of  the  animals,  while  the  other  derives  little  or  none,  but 
on  the  other  hand  suffers  no  injury.  For  example, 
"small  fish  of  the  genus  Nomeus  may  often  be  found 
accompanying  the  beautiful  Portuguese  man-of-war 
(Physalid)  as  it  sails  slowly  about  on  the  ocean's  surface. 
These  little  fish  lurk  underneath  the  float  among  the 
various  hanging  thread-like  parts  of  the  man-of-war  which 
are  provided  with  stinging  cells.  They  are  protected 
from  their  enemies  by  their  proximity  to  these  stinging 
threads,  but  of  what  advantage  to  the  man-of-war  their 
presence  is  is  not  understood."  Similarly  in  the  nests  of 
the  various  species  of  ants  and  termites  many  different 
kinds  of  other  insects  have  been  found.  "  Some  of  these 
are  harmful  to  their  hosts,  in  that  they  feed  on  the  food- 
stores  gathered  by  the  industrious  and  provident  ant,  but 


SOCIAL  AND  COMMUNAL  LIFE  415 

others  appear  to  feed  only  on  refuse  or  useless  substances 
in  the  nest.  Some  may  be  of  help  to  their  hosts  by 
acting  as  scavengers.  Over  one  thousand  species  of  these 
myrmecophilous  (ant-loving)  and  termitophilous  (termite- 
loving)  insects  have  been  recorded  by  collectors  as  living 
habitually  in  the  nests  of  ants  and  termites. ' ' 

Parasitism. — TECHNICAL  NOTE. — As  examples  of  temporary 
external  parasites  find  and  examine  fleas  and  ticks  on  dogs  and  cats, 
red  mites  on  house-flies  and  grasshoppers  (at  the  bases  of  the 
wings),  etc.  As  examples  of  permanent  external  parasites  find 
bird-lice  on  pigeons  or  domestic  fowls  or  on  other  birds.  Note  the 
absence  of  wings  and  the  peculiarly  modified  body  shape  of  these 
parasites.  Examine  a  bird-louse  under  the  microscope  ;  note  the  ab- 
sence of  compound  eyes  (it  has  simple  eyes)  and  absence  of  wings  ; 
note  bits  of  feathers,  its  food,  in  stomach,  showing  through  the 
body.  Find,  as  examples  of  internal  parasites,  intestinal  worms  or 
flukes.  Examine  trichinized  pork  to  see  Trichina  in  muscles.  Ex- 
amine preserved  specimens  of  tapeworms.  Collect  pupae  of  some 
common  butterfly  or  moth  and  keep  them  in  the  schoolroom  until 
either  the  butterflies  or  ichneumon  flies  issue.  Some  will  surely  be 
parasitized,  and  yield  ichneumon  flies  (parasites)  instead  of  a  butter- 
fly. As  examples  of  degeneration  by  quiescence  examine  barnacles 
(found  on  outer  rocks  of  seashore  at  low  tide  ;  easily  obtained  as 
preserved  specimens  by  inland  schools)  and  the  females  of  scale- 
insects.  These  insects  may  be  found  on  oleanders  (the  black  scale, 
Lecanium  olece]  or  fruit-trees  (the  San  Jose  scale,  Aspidiotus  per- 
niciosus}.  Note  the  great  degeneration  of  the  adult  female  of  the 
San  Jose  scale  ;  it  has  no  eyes,  antennae,  wings,  or  legs.  The 
young  may  be  found  crawling  about  at  certain  times  of  the  year ; 
they  have  eyes,  antennae,  and  legs. 

In  addition  to  the  various  ways  of  living  together  among 
animals,  already  described,  namely,  the  social  and  com- 
munal life  of  individuals  of  a  single  species  and  the  com- 
mensal and  symbiotic  life  of  individuals  of  different  species, 
there  is  another  and  very  common  kind  of  association 
among  animals.  This  is  the  association  of  parasite  and 
host;  the  association  between  two  sorts  of  animals  whereby 
one,  the  parasite,  lives  on  or  in  the  other,  the  host,  and  at 
the  expense  of  the  host.  In  this  association  the  parasite 
gains  advantages  great  or  small,  sometimes  even  obtain- 
ing all  the  necessities  of  life,  while  the  host  gains  nothing, 


4i 6  ELEMENTARY  ZOOLOGY 

but  suffers  corresponding  disadvantage,  often  even  the  loss 
of  life  itself.  Parasitism  is  a  phenomenon  common  in 
all  the  large  groups  of  animals,  though  the  parasites 
themselves  are  mostly  invertebrates.  There  are  parasitic 
Protozoa,  worms,  crustaceans,  insects,  and  molluscs,  and 
a  few  vertebrates. 

Some  parasites,  like  the  fleas  and  lice,  live  on  the  sur- 
face of  the  body  of  the  host.  These  are  called  external 
parasites.  Others,  as  the  tapeworms,  live  exclusively 
inside  the  body;  such  are  called  internal  parasites. 
Again,  some,  as  the  bird-lice,  which  are  external  parasites 
feeding  on  the  feathers  of  birds,  spend  their  whole  life- 
time on  the  host;  they  are  called  permanent  parasites. 
Others,  as  a  flea,  which  leaps  on  or  off  its  host  as  caprice 
directs,  or  like  certain  parasites  which  as  young  live  free 
and  active  lives,  finally  attaching  themselves  to  some  host 
and  remaining  fixed  there  for  the  rest  of  their  lives,  are 
called  temporary  parasites.  Such  a  grouping  is  purely 
arbitrary  and  exists  simply  for  the  sake  of  convenience. 
It  is  not  rigid,  nor  does  it  class  parasites  in  their  proper 
natural  groups. 

When  various  parasites  are  examined  it  will  be  noted 
that  practically  in  all  cases  the  body  of  a  parasite  is 
simpler  in  structure  than  the  body  of  other  animals  closely 
related  to  it;  that  is,  species  which  live  parasitically, 
obtaining  their  food  from  and  being  carried  about  by  a 
host,  have  simpler  bodies  than  related  forms  that  live  free 
active  lives,  competing  for  food  with  other  animals  about 
them.  This  simplicity  is  not  primitive,  but  results  from 
the  loss  or  atrophy  of  the  structures  which  the  special 
mode  of  life  of  the  parasite  renders  useless.  Many  para- 
sites are  attached  firmly  by  hooks  or  suckers  to  their  host, 
and  do  not  move  about  independently  of  it.  They  have 
no  need  of  the  power  of  locomotion,  and  accordingly  are 
usually  without  wings,  legs,  or  other  locomotory  organs. 


SOCIAL   AMD  COMMUNAL  LIFE  4*1 

Because  they  have  no  need  of  locomotion  they  have  no 
need  of  organs  of  orientation,  those  special  sense  organs 
like  the  eyes,  ears,  and  feelers  which  serve  to  guide  and 
direct  the  moving  animal ;  and  most  fixed  parasites  will 
be  found  to  have  no  eyes,  or  any  of  those  organs  acces- 
sory to  locomotion,  and  which  serve  for  the  detection  of 
food   or   of  enemies.      Because    these   important  organs, 
which  depend  for  their  successful  activity  on  a  well-organ- 
ized nervous  system,  are  lacking,  the  nervous  system  of 
parasites    is    usually    very    simple.      Again,   because  the 
parasite  usually  feeds  on  the  already  digested  food  or  the 
blood  of  its  host,  most  parasites  have  a  very  simple  ali- 
mentary canal,  or  even  none  at  all.    Finally,  as  the  fixed 
parasite  leads  a  wholly  sedentary  and  inactive  life,   the 
breaking  down  and  rebuilding  of  tissue  in  its  body  goes 
on  very  slowly  and  in  minimum  degree,  so  that  there  is 
little  need  of  highly  developed  respiratory  and  circulatory 
systems;  and  most  fixed  and  internal  parasites  have  these 
systems  of  organs  decidedly  simplified.      Altogether  the 
body  of  a  fixed  permanent  parasite  is  so  simplified  and  so 
wanting  in  all  those  special  structures  which  characterize 
the  active,  complex  animals  that  it  often  presents  a  very 
different  appearance  from  those  forms  with  which  we  know 
it  to  be  nearly  related.      This  simplicity  due  to  loss  or 
reduction  of  parts  is  called  degeneration.     Such  simplicity 
of  body-structure  due  to  degeneration  is,  however,  essen- 
tially different  in  its  origin  from  the  simplicity  of  the  lower 
simpler  animals.      In  them  the  simplicity  of  body  is  prim- 
itive;   they   are    generalized    animals;    the    simplicity   of 
degeneration  is  acquired;    it  is  really  an  adaptation,   or 
specialization. 

An  excellent  example  of  body  degeneration  due  to  the 
adoption  of  a  parasitic  habit  is  that  of  Sacculina  (fig.  159), 
a  crustacean  parasitic  on  other  crustaceans,  namely,  crabs. 
The  young  Sacculina  is  an  active,  free-swimming  larva 


4i«  ELEMENTARY  ZOOLOGY 

essentially  like  a  young  prawn  or  crab.  After  a  short 
period  of  independent  existence  it  attaches  itself  to  the 
abdomen  of  a  crab,  and  lives  as  a  parasite.  It  completes 
its  development  under  the  influence  of  this  parasitic  life, 
and  when  adult  bears  absolutely  no  resemblance  to  such 


FIG.  159.  —  Sacculina.  a  parasitic  crustacean;  A,  attached  to  a  crab,  the 
root-like  processes  of  the  parasite  penetrating  the  body  of  the  host;  B, 
the  active  larval  condition;  C,  the  adult  removed  from  its  host.  (After 
Haeckel.) 

a  typical  crustacean  as  a  crab  or  crayfish.  Its  body  ex- 
ternal to  the  host  crab  is  simply  a  pulsating  tumor-like 
sac,  with  no  mouth-parts,  no  legs,  and  internally  hardly 
any  well-developed  organs  except  those  of  reproduction. 
Degeneration  here  is  carried  very  far. 


SOCIAL  AND  COMMUNAL  LIFE  4 '9 

Various  parasites  have  been  referred  to  in  Part  II  under 
their  proper  branch  and  class.  The  worms  include  an 
unusually  large  number  of  them,  such  as  the  tape- 
worms, trichinae  and  other  intestinal  forms,  all  of  which 
live  as  internal  parasites  in  the  alimentary  canal  or  in 
other  organs  of  higher  animals,  especially  the  vertebrates. 
Many  crustaceans  are  parasitic,  usually  living,  like  the 
fish-lice,  as  fixed  external  parasites  on  fishes,  other  crus- 
taceans, etc.,  but  with  a  free  and  active  larval  stage. 
Among  the  insects,  on  the  contrary,  many  of  the  parasitic 
forms  (as  the  ichneumon  flies)  are  free  and  active  in  the 
adult  stage,  but  live  as  internal  grubs  or  maggots  in  the 
larval  stage.  The  ichneumon  flies  (of  the  order  Hymen- 
optera)  are  four-winged,  slender-bodied  insects  which 
lay  their  eggs  either  on  or  in  (by  means  of  a  sharp  pierc- 
ing ovipositor)  some  caterpillar  or  beetle  grub,  into  the 
body  of  which  the  young  grub-like  ichneumon  larvae 
burrow  on  hatching.  The  parasites  feed  on  the  body- 
tissues  of  the  host,  not  attacking,  however,  such  organs 
as  the  heart  or  nervous  system,  which  would  produce  the 
immediate  death  of  the  host.  The  caterpillar  lives  with 
the  ichneumon  grubs  within  it  usually  until  nearly  time 
for  its  pupation.  Often,  indeed,  it  pupates  with  the  para- 
site still  in  its  body.  But  it  never  comes  to  maturity. 
The  larval  ichneumons  pupate  either  within  the  body  of 
its  host,  or  in  a  tiny  silken  cocoons  outside  of  its  body 
(fig.  1 60).  From  the  cocoons  the  winged  adult  ichneu- 
mons issue;  and  after  mating  the  females  find  another 
caterpillar  on  whose  body  to  lay  their  eggs. 

Degeneration  can  be  produced  by  other  causes  than 
parasitism.  It  is  evident  that  if  for  any  other  reason  an 
animal  should  adopt  an  inactive  fixed  life  it  would  degen- 
erate. The  barnacles  (see  fig.  37)  are  excellent  examples 
of  degeneration  through  quiescence.  They  are  crustaceans 
related  most  nearly  to  the  crabs  and  shrimps.  The 


420 


ELEMENTARY  ZOOLOGY 


young  barnacle  just  from  the  egg  is  a  six-legged,  free- 
swimming  larva  (nauplius)  with  a  single  eye,  greatly  like 
a  young  prawn  or  crab.  It  develops  during  its  independ- 
ent life  two  compound  eyes  and  two  large  antennae.  But 

soon  it  attaches  itself  to  some 
stone  or  shell,  or  pile  or  ship's 
bottom,  giving  up  its  power  of 
locomotion,  and  its  further  de- 
velopment is  a  degeneration.  It 
loses  its  compound  eyes  and  an- 
tennae, and  acquires  a  protecting 
shell.  Its  swimming  feet  become 
modified  into  grasping  organs, 
and  it  loses  most  of  its  outward 
resemblance  to  the  typical  mem- 
bers of  its  class.  The  Tunicata 
or  ascidians  compose  a  whole 
group  of  animals  which  are  fixed 
in  their  adult  condition  and  have 
thus  become  degenerate.  They 
have  been  likened  to  a  "mere 
rooted  bag  with  a  double  neck. " 
In  their  young  stage  they  are 
free-swimming,  active,  tadpole- 
like  or  fish -like  larvae,  possessing 
(From  organs  much  like  those  of  the 
adult  simplest  fish  or  fish-like 
animals.  Their  larval  structure  reveals,  however,  the 
relationships  of  the  ascidians  to  the  vertebrates,  a  rela- 
tionship which  is  not  at  all  apparent  in  the  degenerate 
adults.  Certain  insects  live  sedentary  or  fixed  lives.  All 
the  members  of  one  large  family,  the  Coccidae,  or  scale- 
insects  (figs.  62  and  63),  have  females  which  as  adults  are 
wingless  and  in  some  cases  have  no  legs,  eyes,  or  antennae, 
while  the  males  are  all  winged  and  have  legs  and  the 


sitic  ichneumon  fly. 
specimen. ) 


SOCIAL   AND   COMMUNAL   LIFE  421 

special  sense  organs.  The  males  lead  a  free  active  life, 
but  the  females  have  nearly  or  quite  given  up  the  power 
of  locomotion,  attaching  themselves  by  means  of  their 
sucking  beak  to  some  plant,  where  they  obtain  a  suffi- 
cient food-supply  (plant-sap)  and  lay  their  eggs.  In  both 
males  and  females  the  larvae  are  little  active  crawling  six- 
legged  creatures  with  legs,  eyes,  and  antennae. 

We  are  accustomed  perhaps  to  think  of  degeneration 
as  necessarily  implying  a  disadvantage  in  life.  It  is  true 
that  a  blind,  footless,  degenerate  animal  could  not  cope 
with  the  active,  keen-sighted,  highly  organized  non- 
degenerate  in  free  competition.  But  free  competition  is 
exactly  what  the  degenerate  animal  has  nothing  to  do 
with.  Certainly  the  Sacculina  and  the  scale-insects  live 
well ;  they  are  admirably  adapted  to  the  kind  of  life  they 
lead.  A  parasite  enjoys  certain  obvious  advantages  in  life, 
and  even  extreme  degeneration  is  no  drawback  (except  as 
we  shall  see  later),  but  gives  it  a  body  which  demands  less 
food  and  care.  As  long  as  the  host  is  successful  in  elud- 
ing its  enemies  and  avoiding  accident  and  injury  the  para- 
site is  safe.  Its  life  is  easy  as  long  as  the  host  lives. 
But  the  disadvantages  of  parasitism  and  degeneration  are 
nevertheless  obvious.  The  fate  of  the  parasite  is  bound 
up  with  the  fate  of  the  host.  "  When  the  enemy  of  the 
host  crab  prevails,  the  Sacculina  goes  down  without  a 
chance  to  struggle  in  its  own  defence.  But  far  more  im- 
portant than  the  disadvantage  in  such  particular  or  indi- 
vidual cases  is  the  fact  that  the  parasite  cannot  adapt  itself 
in  any  considerable  degree  to  new  conditions.  It  has 
become  so  modified,  so  specialized  to  adapt  itself  to  the 
very  special  conditions  under  which  it  now  lives,  it  has 
gone  so  far  in  giving  up  organs  and  functions,  that  if 
present  conditions  change  and  new  ones  come  to  exist 
the  parasite  cannot  adapt  itself  to  them.  The  independ- 
ent free-living  animal  holds  itself,  one  may  say,  able  and 


ELEMENTARY  ZOOLOGY 


if 


SOCIAL  AND  COMMUNAL   LIFE  423 

ready  to  adapt  itself  to  any  new  conditions  of  life.  The 
parasite  has  risked  everything  for  the  sake  of  a  sure  and 
easy  life  under  the  present  existing  conditions.  Change 
of  conditions  means  its  extinction." 

For  an  elementary  account  of  commensalism  and  para- 
sitism see  Jordan  and  Kellogg 's  "  Animal  Life,"  pp.  172- 
200.  The  account  here  given  is  based  on  the  author's 
previously  written  account  in  "  Animal  Life."  See  also 
Van  Beneden's  "  Animal  Parasites  and  Messmates." 


CHAPTER    XXXI 
COLOR    AND    PROTECTIVE    RESEMBLANCES 

TECHNICAL  NOTE. — For  an  appreciation  of  the  reality  of  pro- 
tective resemblances  observations  must  be  made  in  the  field.  Ex- 
amples are  easily  found.  Locusts,  katydids,  green  caterpillars, 
lizards,  crouching  rabbits,  and  brooding  birds  are  readily  observed 
instances  of  general  protective  resemblance.  For  examples  of 
variable  resemblance  examine  specimens  of  a  single  locust  species 
taken  from  different  localities  ;  the  individuals  of  the  various  species 
of  the  genus  Irimerotropis  show  much  variation  to  harmonize 
with  their  surroundings.  Collect  a  number  of  larvae  (caterpillars)  of 
one  of  the  swallow-tail  butterflies  (Papilla},  and  when  ready  to 
pupate  put  them  separately  into  pasteboard  boxes  lined  inside  with 
differently  colored  paper.  The  chrysalids  will  show  in  their  colora- 
tion the  influence  of  the  different  colors  of  the  lining  paper,  their 
immediate  environment.  As  examples  of  special  protective  resem- 
blance observe  inch-  or  span-worms  (larvas  of  Geometrid  moths). 
The  walking-stick  is  not  uncommon  ;  many  spiders  that  inhabit 
flower-cups  show  striking  protective  color  patterns  ;  and  the 
Graptas  or  comma-butterflies  which  resemble  dead  leaves  may  be 
examined. 

To  illustrate  warning  colors,  find,  if  possible,  the  larvae  (cater- 
pillars) of  the  common  milkweed  or  monarch  butterfly  (Anosia 
plexippus],  and  offer  them  to  birds,  at  the  same  time  offering  other 
caterpillars,  and  note  the  results.  For  terrifying  or  threatening 
appearance  find  specimens  of  the  large  green  tobacco-  or  tomato- 
worm  (larva  of  the  five-spotted  sphinx-moth,  Phlegethontius  caro- 
/ina),  or  other  sphingid  larvae. 

The  butterflies  illustrating  the  striking  example  of  mimicry,  de- 
scribed on  p.  432,  can  be  found  in  most  parts  of  the  country. 
Syrphid  and  other  flies  which  mimic  bees  and  wasps  can  readily 
be  found  on  flowers. 

Each  student  should  search  for  himself  for  examples  of  pro- 
tective resemblance. 

Use  of  color. — The  prevalence  of  color  and  the  often- 
times striking  and  intricate  coloration  patterns  of  animals 

424 


COLOR  AND  PROTECTIVE  RESEMBLANCES  425 

demand  some  explanation.  As  naturalists  are  accustomed 
to  find  the  frequently  bizarre  and  seemingly  inexplicable 
shapes  and  general  structure  of  animals  readily  explained 
by  the  principle  of  adaptation,  that  is,  special  modification 
of  body-structure  to  fit  special  conditions  of  life,  so  they 
look  to  use  as  the  chief  explanation  of  color  and  markings. 
Some  uses  are  obvious ;  bright  colors  and  striking  patterns 
may  serve  to  attract  mates  or  to  avail  as  recognition 
marks  by  which  individuals  of  a  kind  may  readily  recog- 
nize each  other.  The  white  color  of  arctic  animals  prob- 
ably serves  to  help  keep  them  warm  by  preventing 
radiation  of  heat  from  the  body;  on  the  other  hand  dark 
color  may  also  help  to  keep  animals  warm  by  absorbing 
heat.  ' '  But  by  far  the  most  widespread  use  of  color  is 
for  another  purpose,  that  of  assisting  the  animal  in  escap- 
ing from  its  enemies  or  in  capturing  its  prey. ' ' 

It  is  common  knowledge  that  the  young  and  old,  too, 
of  many  kinds  of  ground-inhabiting  animals,  when  startled 
by  an  enemy  will  not  run,  but  crouching  close  to  the 
ground  remain  immovable,  trusting  to  remain  unper- 
ceived.  But  a  blue  or  crimson  rabbit,  however  still  it 
might  keep,  would  be  easily  seen  by  its  enemy  and  killed. 
Rabbits,  however,  which  are  good  examples  of  animals 
having  this  habit  of  lying  close,  are  neither  blue  nor  green 
nor  red,  but  are  colored  very  much  like  the  ground  on 
which  they  crouch.  This  harmonious  coloration  is  as 
necessary  to  the  success  of  this  habit  as  is  the  keeping 
still.  A  grasshopper  flying  or  leaping  in  the  air  is  con- 
spicuous ;  when  it  alights  how  inconspicuous  it  is !  Unless 
one  has  followed  it  closely  in  its  flight  and  has  kept  the 
eye  fixed  on  it  after  alighting  it  is  usually  impossible  to 
distinguish  it  from  its  surroundings.  And  this  is  greatly 
to  the  advantage  of  the  grasshopper  in  its  efforts  to 
escape  its  enemies,  that  is,  in  its  struggle  for  existence. 
On  the  other  hand  a  green  katydid  would  be  very  con- 


426  ELEMENTARY  ZOOLOGY 

spicuous  in  a  dusty  road.  But  dusty  roads  are  precisely 
where  katydids  do  not  rest.  They  alight  among  the 
green  leaves  of  a  tree  or  shrub.  The  animals  that  live  in 
deserts  are  almost  all  obscurely  mottled  with  gray  and 
brownish  and  sand-color  so  as  to  harmonize  in  color  with 
their  habitual  environment.  The  arctic  hares  and  foxes 
and  grouse  which  live  in  regions  of  perpetual  snow  are 
pure  white  instead  of  red  or  brown  or  gray  like  their 
cousins  of  temperate  and  warm  regions. 

These  cases  of  an  animal's  color  and  markings  har- 
monizing with  the  usual  environment  are  called  instances 
of  protective  resemblance ;  that  is,  they  are  resemblances 
for  a  purpose,  that  purpose  being  to  render  the  animal  in- 
distinguishable from  its  surroundings  and  thus  to  aid  it  in 
escaping  its  enemies.  Such  protective  resemblances  are 
obviously  of  great  value  to  animals,  and,  like  other 
advantageous  modifications,  have  been  produced  by  the 
action  of  natural  selection.  Those  individuals  of  a  species 
most  conspicuous  and  hence  most  readily  perceived  by 
enemies  are  the  first  (under  ordinary  circumstances)  to 
be  captured  and  eaten.  The  less  conspicuous  live  and 
produce  young  like  themselves.  Of  these  young  the  least 
conspicuous  are  again  saved  and  so  over  and  over  again 
through  thousands  of  generations  until  this  natural  select- 
ing of  the  protectively  colored  results  in  the  production 
of  the  wonderfully  specialized  examples  of  resemblance 
to  which  attention  is  called  in  the  following  paragraphs. 

General,  variable,  and  special  protective  resemblance. 
— In  the  brooks  most  fishes  are  dark  olive  or  greenish 
above  and  white  below.  To  the  birds  and  other  enemies 
which  look  down  on  them  they  are  colored  like  the 
bottom.  To  their  fish-enemies  which  look  up  from  below 
they  are  like  the  white  light  above  them  in  color  and  their 
forms  are  not  clearly  seen.  The  green  tree-frogs  and 
tree-snakes  which  live  habitually  among  green  foliage; 


COLOR  AND  PROTECTIVE  RESEMBLANCES 


427 


the  mottled  gray  and  tawny  lizards  and  birds  and  small 
mammals  of  the  plains  and  deserts,  and  the  white  hares  and 
foxes  and  owls  and  ptar- 
migan of  the  snowy  arctic 
regions — all  show  a  gener- 
al protective  resemblance. 
Sometimes  an  animal 
changes  color  when  its  sur- 
roundings change.  Certain 
hares  and  grouse  of  north- 
ern latitudes  are  white  in 
winter  when  the  snow 
covers  all  the  ground,  but 
in  summer  when  much  of 
the  snow  melts,  revealing 
the  brown  and  gray  rocks 
and  withered  leaves,  they 
put  on  a  grayish  and 
brownish  coat  of  hair  or 
feathers.  A  small  insect 
called  the  toad-bug  (Gal- 
gulus}  lives  abundantly  on 
the  banks  of  a  pond  on  the 
campus  of  Stanford  Uni- 
versity. The  shores  of 
this  pond  are  covered  in 
some  places  with  bits  of 
bluish  rock,  in  others  with 
bits  of  reddish  rock,  and 
in  still  others  with  sand. 

c  r  j  FIG.  162. — The  twig  or   walking-stick 

Specimens  Ot  the  toad- bug  insect,  Diapheromera  femorata. 
Collected  from  the  blue  (From  specimen.) 

rocks  are  bluish  or  leaden  in  color,  those  from  the  red  rocks 
are  reddish,  and  those  from  the  sand  are  sand-colored. 
Changes  of  color  to  suit  the  surroundings  can  be  quickly 


42  S  ELEMENTARY  ZOOLOGY 

made  by  some  animals.  The  chameleons  of  the  tropics 
change  momentarily  from  green  to  brown,  blackish,  or 
golden.  There  is  a  little  fish  (Oligocottns  snyderi]  com- 
mon in  the  tide-pools  of  the  Bay  of  Monterey  in  California 
whose  color  changes  quickly  to  harmonize  with  the  rocks 
it  happens  to  rest  above.  Such  changing  coloration  to 
suit  the  surroundings  may  be  called  variable  protective 
resemblance. 

Very  striking  are  those  cases  of  protective  resemblance 
in  which  the  animal  resembles  in  color  and  shape,  some- 
times in  extraordinary  detail,  some  particular  object  or 
part  of  its  usual  environment.  This  may  be  called  special 
protective  resemblance.  The  larvae  of  the  Geometrid 
moths  called  inch-worms  or  span-worms  are  twig-like  in 
appearance,  and  have  the  habit,  when  disturbed,  of  stand- 
ing out  stiffly  from  the  twig  or  branch  on  which  they  rest, 
so  as  to  resemble  in  attitude  as  well  as  color  and  mark- 
ings a  short  or  broken  twig.  To  increase  this  simulation 
the  body  of  the  larva  often  has  a  few  irregular  spots  or 
humps  resembling  the  scars  left  by  fallen  leaves,  and  it 
also  lacks  the  middle  prop-legs  of  the  body  common  to 
other  lepidopterous  larvae,  which  would  tend  to  destroy 
the  illusion  so  successfully  carried  out  by  it.  The  common 
twig-insect  or  walking-stick  (fig.  162)  with  its  wingless, 
greatly  elongate,  brown  or  greenish  body  and  legs  is  when 
at  rest  quite  indistinguishable  from  the  twigs  on  which  it 
lies.  Another  excellent  example  of  special  protective 
resemblance  is  furnished  by  the  famous  green-leaf  insect 
(Phylliuwi]  of  the  tropics,  which  has  broad  leaf-like  wings 
and  body  of  a  bright  green  color  with  markings  which 
imitate  the  leaf-veins,  and  small  irregular  yellowish  spots 
which  simulate  decaying  or  stained  or  fungus-covered 
spots  in  the  leaf.  Most  striking  of  all,  however,  is  the 
large  dead-leaf  butterfly  Kallima  (fig.  163)  of  the  East 
Indian  region.  The  upper  sides  of  the  wing  are  dark 


COLOR  AND  PROTECTIVE  RESEMBLANCES  4*9 


FlG.    163. — The   dead-leaf  butterfly,    Kallima    sp.,    a  remarkable  case  of 
special  protective  resemblance.     (From  specimen.) 


43°  ^ELEMENTARY  ZOOLOGY 

with  purplish  and  orange  markings  not  at  all  resembling 
a  dead  leaf.  But  the  butterflies  when  at  rest  hold  their 
wings  together  over  the  back,  so  that  only  the  under  sides 
of  them  are  exposed.  These  are  exactly  the  color  of  a 
dry  dead  leaf  with  markings  mimicking  midrib  and 
oblique  veins,  and,  most  remarkable  of  all,  what  are 
apparently  two  holes  like  those  made  in  leaves  by  insects, 
but  in  the  butterfly  imitated  by  two  small  circular  spots 
free  from  scales  and  hence  clear  and  transparent.  When 
Kallima  alights  it  holds  the  wings  in  such  position  that  the 
combination  of  all  four  produces  with  remarkable  fidelity 
the  simulation  of  a  dead  leaf  still  attached  to  the  twig  by 
a  short  pedicel  or  leaf-stalk  (imitated  by  a  short  ' '  tail 
on  the  hind  wings).  The  head  and  legs  of  the  butterfly 
are  concealed  beneath  the  wings. 

Warning  colors,  terrifying  appearances,  and  mimicry. 
— While  many  animals  are  so  colored  as  to  harmonize 
with  their  habitual  or  usual  environment,  others  on  the 
contrary  are  very  brightly  colored  and  marked  in  such 
bizarre  and  striking  pattern  as  to  be  conspicuous.  There 
is  no  attempt  at  concealment;  it  is  obvious  that  conspicu- 
ousness  is  the  object  sought  or  at  least  produced  by  the 
coloration.  Animals  like  these,  we  shall  find,  are  in 
almost  all  cases  specially  protected  by  special  weapons  of 
defence  such  as  stings  or  poison-fangs,  or  by  the  secretion 
of  an  acrid,  ill-tasting  fluid  in  the  body.  Many  cater- 
pillars have  been  found,  by  observation  in  nature  and  by 
experiment,  to  be  distasteful  to  insectivorous  birds.  Now 
it  is  obvious  that  it  would  be  advantageous  to  these  cater- 
pillars to  be  readily  recognized  by  birds.  After  a  few 
trials  the  bird  learns  by  experience  to  let  these  distasteful 
larvae  alone ;  their  conspicuous  markings  serve  as  warning 
colors.  The  black-and-yel low-banded  caterpillar  of  the 
common  milkweed  or  monarch  butterfly  (A nosia  plexip- 
)  is  a  good  example  of  such  protection  by  a  combina- 


COLOR  AND  PROTECTIVE  RESEMBLANCES 


43* 


tion  of  distastefulness  and  warning  coloration.  The  little 
lady-bird  beetles  are  mostly  distasteful  to  birds ;  they  are 
brightly  and  conspicuously  marked.  Certain  little  Nica- 
raguan  frogs  have  a  bright  livery  of  red  and  blue,  in  strong 


FlG.  164. — The  larva  of  the  pen-marked  sphinx-moth,  Sphinx  chersis, 
showing  terrifying  attitude,     (After  Comstock.) 

contrast  to  the  dull  concealing  colors  of  other  frogs  in 
their  region.  By  offering  these  little  blue  and  red  frogs 
to  hens  and  ducks  the  naturalist  Belt  found  that  they  are 
distasteful  to  the  birds. 

Certain  animals  which  are  without  special  means  of 
defence  and  are  not  distasteful  are  yet  so  marked  or 
shaped,  and  so  behave  as  to  present  a  threatening  or 
terrifying  appearance.  The  large  green  caterpillars  of 
the  sphinx-moths,  the  tomato-  and  tobacco-worms,  are 


432  ELEMENTARY  ZOOLOGY 

familiar  examples,  each  larva  having  a  sharp  horn  on  the 
back  of  the  next  to  last  body-segment  (fig.  164).  When 
disturbed  the  caterpillar  assumes  a  threatening  attitude, 
and  the  horn  seems  to  be  an  effective  weapon  of  defence. 
As  a  matter  of  fact  it  is  not  at  all  a  weapon  of  defence, 
being  weak,  not  provided  with  poison,  and  altogether 
harmless. 

But  it  would  plainly  be  to  the  advantage  of  a  defence- 
less animal,  one  without  poison-fangs  or  sting  and  without 
an  ill-tasting  substance  in  its  body,  to  be  so  marked  and 
shaped  as  to  mimic  some  other  specially  defended  or 
inedible  animal  sufficiently  to  be  mistaken  for  it  and  thus 
to  escape  attack.  Such  cases  have  been  noted,  especially 
among  insects.  This  kind  of  protective  resemblance  may 
be  called  mimicry.  A  most  striking  case  is  that  presented 
by  the  familiar  monarch  and  viceroy  butterflies  (fig.  165). 
The  monarch  (Anosia  plexippus)  is  perhaps  the  most 
abundant  and  widespread  butterfly  of  our  country.  It  is 
a  fact  well  known  to  entomologists  that  it  is  distasteful  to 
birds  and  is  let  alone  by  them.  It  is  conspicuous,  being 
large  and  chiefly  red-brown  in  color.  The  viceroy 
(Basilarchia  archippus),  also  red-brown  and  patterned 
almost  exactly  like  the  monarch,  is  not,  as  its  appearance 
would  seem  to  indicate,  a  very  near  relation  of  the  latter, 
but  on  the  contrary  it  belongs  to  a  genus  of  butterflies 
all  of  which,  except  the  viceroy  and  one  other,  are  black 
and  white  in  color  and  of  different  pattern  from  the 
monarch.  The  viceroy  is  not  distasteful  to  birds,  but  by 
its  extraordinary  simulation  or  mimicking  of  the  monarch 
it  is  not  distinguished  from  it  and  so  is  not  molested.  In 
the  tropics  there  have  been  discovered  numerous  examples 
of  mimicry  among  insects.  The  members  of  two  large 
families  of  butterflies  ^Danaidae  and  Heliconida?)  are  dis- 
tasteful to  birds  and  are  mimicked  by  members  of  other 
butterfly  families  .(especially  the  Pieridae). 


COLOR  AND  PROTECTIVE  -RESEMBLANCES  433 

Alluring  coloration. — A  few  animals  show  what  is 
called  alluring  coloration ;  that  is,  they  display  a  color 
pattern  so  arranged  as  to  resemble  or  mimic  a  flower  or 
other  lure,  and  thus  entice  to  them  other  animals,  their 


FIG.  165. — The  monarch  butterfly,  Anosia  plexippiis  (above),  distasteful  to 
birds,  and  the  viceroy,  Basilarchia  archippus  (below),  which  mimics  it. 
From  specimens.) 

natural  prey.  Certain  Brazilian  fly-catching  birds  have  a 
brilliantly  colored  crest  which  can  be  displayed  in  the 
shape  of  a  flower-cup.  The  insects  attracted  by  the  false 
flower  furnish  the  bird  with  food.  In  the  tribe  of  fishes 
called  the  "anglers"  or  "  fishing  frogs,"  the  front  rays 
of  the  dorsal  fin  are  prolonged  in  the  shape  of  long  slender 
filaments,  the  foremost  and  longest  of  which  has  a  flat- 
tened and  divided  extremity.  The  angler  conceals  itself 
in  the  mud  or  in  the  cavities  of  a  coral  reef,  and  waves 
the  filament  back  and  forth.  Small  fish  are  attracted 


434 


ELEMENTARY  ZOOLOGY 


by  the  lure,  mistaking  it  for  worms  writhing  about.  When 
they  approach  they  are  engulfed  in  the  mouth  of  the 
angler,  which  in  some  species  is  of  enormous  size.  One 
of  these  angler  species  is  known  to  fishermen  as  the 
"  all-mouth." 

For  a  fuller  account  of  protective  resemblances  and 
mimicry  see  Jordan  and  Kellogg's  "Animal  Life,"  pp. 
201-223.  For  still  more  extended  accounts  see  Poulton's 
"  Colours  of  Animals,  "  and  Beddard's  "  Animal  Colora- 
tion." 


CHAPTER    XXXII 
THE    DISTRIBUTION    OF    ANIMALS 

TECHNICAL  NOTE. — The  larger  aspects  or  phenomena  of  the  dis- 
tribution of  animals  over  the  earth  on  land  and  in  sea  cannot  be 
studied  personally  in  the  field  by  the  student,  but  many  local  fea- 
tures of  distribution  can  be  so  observed  and  studied.  The  restric- 
tion of  certain  kinds  of  animals  to  certain  kinds  of  habitat,  the 
presence  and  character  and  effectiveness  of  barriers,  some  of  the 
modes  of  distribution,  the  presence  and  successful  life  of  introduced 
foreign  species  such  as  the  black  and  brown  rats,  the  English 
sparrow,  the  German  and  Asiatic  cockroaches,  the  gradual  change 
of  range  or  distribution  of  certain  kinds  of  animals  through  the  in- 
fluence of  a  change  in  environment  (caused  by  man  in  cutting  off 
forests,  cultivating  heretofore  wild  pastures,  etc.)  all  offer  favorable 
and  profitable  opportunities  for  personal  observation. 

An  excellent  and  feasible  piece  of  field-work  in  distribution  is  the 
making  of  a  zoological  survey  of  the  locality  in  which  the  school  is 
situated.  A  map  of  the  locality  should  be  made  on  a  generous 
scale,  which  should  include  all  prominent  physical  features  of  the 
region,  such  as  streams,  ponds,  hills,  woodlands,  marshes,  etc., 
and  on  this  map  should  be  indicated  the  places  where  the  various 
animals  of  the  local  fauna  occur.  Some  of  the  animal  species  will 
have  a  limited  range,  and  the  limits  of  this  range  should  be  shown. 
This  map  and  faunal  list  can  be  added  to  and  perfected  by  succes- 
sive classes.  For  fuller  discussions  of  the  geographical  distribution 
of  animals  see  Jordan  and  Kellogg 's  "  Animal  Life,"  Beddard's  "  Zoo- 
geography," Heilprin's  "  The  Distribution  of  Animals,"  and  Wallace's 
"Geographical  Distribution." 

Geographical  distribution. — It  is  a  matter  of  common 
knowledge  with  all  of  us  that  there  are  no  wild  lions  or 
camels  or  kangaroos  or  monkeys  or  ostriches  or  night- 
ingales in  North  America.  Ostriches  are  found  only  in 
Africa  and  South  America,  kangaroos  only  in  Australia, 


43^  ELEMENTARY  ZOOLOGY 

lions  only  in  Asia  and  Africa.  On  the  other  hand  there 
are  no  opossums  in  Europe  or  grizzly  bears  or  rattlesnakes 
anywhere  else  in  the  world  than  in  this  country.  That 
is,  certain  kinds  of  animals  have  a  certain  limited  range  of 
occurrence  or  distribution.  It  is  obvious,  too,  that  certain 
animals  live  only  on  land,  while  others  live  only  in  water, 
and  of  these  latter  some  are  restricted  to  the  ocean,  while 
others  live  only  in  fresh  water.  All  of  the  facts  regard- 
ing the  dispersion  or  diffusion  of  animals  on  land  and  in 
water  make  up  the  science  of  the  geographical  distribution 
of  animals,  or,  as  it  is  sometimes  called,  zoogeography. 
Under  this  subject  are  included  not  only  the  facts  of  the 
present  actual  distribution  or  occurrence  of  animals  over 
the  world,  but  the  facts  concerning  the  reasons  for  this 
distribution,  the  modes  of  travel  and  dispersion,  the  char- 
acter and  influence  of  barriers  to  the  spread,  and  the 
results,  in  the  adaptation  of  old  forms  and  the  production 
of  new  forms,  of  the  phenomena  of  distribution. 

Just  as  maps  are  made  to  show  graphically  the  facts  of 
political  geography,  which  concerns  the  position  and 
extent  of  the  various  powers  and  States  which  claim 
the  allegiance  of  the  people,  and  the  facts  of  physical 
geography,  which  concerns  the  physical  character  of  the 
earth's  surface,  so  maps  are  made  to  show  the  geograph- 
ical distribution  of  animals.  Because  of  the  great  numbers 
of  animal  species  no  one  map  can  show  the  distribution 
of  all  species,  but  a  series  of  maps  of  the  world  or  of  a 
continent  or  of  a  State  or  county  or  more  limited  region 
could  be  made  (and  many  such  have  been  made)  showing 
the  distribution  of  selected  species.  In  a  map  of  a  limited 
locality,  say  of  a  few  square  miles,  the  occurrence  and 
distribution  of  most  of  the  commoner  and  more  familiar 
animals  can  be  shown,  and  each  high  school  should 
possess  such  a  map  (see  technical  note  at  beginning  of 
this  chapter). 


THE  DISTRIBUTION  OF  ANIMALS  437 

Laws  of  distribution. — The  laws  governing  the  distri- 
bution of  animals  over  the  earth's  surface  have  been 
recently*  expressed  in  a  simple  statement  as  follows: 
Every  species  of  animal  is  found  in  every  part  of  the  earth 
unless  (a)  its  individuals  have  been  unable  to  reach  this 
region  on  account  of  barriers  of  some  sort;  or  (^)  having 
reached  it,  the  species  is  unable  to  maintain  itself,  through 
lack  of  capacity  for  adaptation,  through  severity  of  com- 
petition with  other  forms,  or  through  destructive  conditions 
of  environment;  or  (c)  having  entered  and  maintained 
itself  it  has  become  so  altered  in  the  process  of  adaptation 
as  to  become  a  species  distinct  from  the  original  type. 

Modes  of  migration  and  distribution. — That  animals 
should  be  continually  trying  to  extend  their  range  is 
obvious  from  what  we  know  of  their  rapid  increase  by 
multiplication.  In  a  region  which  can  provide  food  for 
but  one  thousand  wolves,  there  is  a  production  each  year 
of  several  times  one  thousand.  These  new  wolves  must 
struggle  among  themselves  for  food,  or  migrate,  if  possi- 
ble, to  new  regions  as  yet  not  inhabited  by  wolves.  The 
wolfs  mode  of  migration  or  distribution  is  walking  or 
running,  and  so  with  other  mammals  except  the  bats  and 
aquatic  forms.  Birds  and  bats  can  fly,  and  can  thus 
migrate  more  swiftly,  farther,  and  over  barriers  which 
would  stop  mammals.  Most  insects  can  fly.  Worms 
can  only  crawl  and  very  slowly  at  that.  Fishes  can  swim, 
but  if  they  are  in  a  landlocked  sheet  of  water,  they  cannot 
go  beyond  its  confines.  Marine  animals  can  migrate 
from  ocean  to  ocean,  and  land  animals  from  continent  to 
continent  unless  checked  by  barriers  (see  next  para- 
graph). 

But  besides  such  voluntary  and  independent  modes  of 
distribution  long  journeyings  may  be  made  involuntarily, 
or  by  a  passive  migration  as  it  may  be  called.  Parasites, 

*  Jordan  and  Kellogg's  "  Animal  Life,"  1900,  p.  274. 


43 8  ELEMENTARY  ZOOLOGY 

for  example,  are  carried  by  their  hosts  in  all  their  travels ; 
the  tiny  Tardigrada  and  Rotifera,  which  can  be  desiccated 
and  yet  restored  to  active  life  by  coming  again  into  water, 
are  carried  in  the  dried  mud  on  the  feet  of  birds  or  other 
animals.  On  floating  objects  in  rivers  or  in  ocean  cur- 
rents land-animals  may  be  carried  long  distances.  Man, 
the  greatest  traveller  of  all,  is  responsible  for  the  widened 
distribution  of  many  animals.  Thus  have  come  to  us  in 
ships  from  Europe  the  black  and  brown  rats,  the  English 
sparrow,  the  Hessian  fly,  the  commonest  cockroaches  of 
our  houses  and  many  other  forms.  And  these  animals 
have  been  carried  involuntarily  all  over  the  United  States 
in  railway-cars  and  wagons. 

Barriers  to  distribution. — As  is  indicated  in  the  para- 
graph on  the  modes  of  migration,  a  considerable  sheet  of 
water  is  obviously  a  barrier  to  the  further  travelling  of  a 
walking  or  crawling  land-animal,  although  no  barrier  to 
a  winged  form.  Similarly  a  strip  of  land  is  a  barrier  to  a 
strictly  aquatic  animal  as  a  fish.  Or  a  high  fall  in  the 
stream  may  serve  as  an  insuperable  barrier,  making  it  im- 
possible for  any  fish  below  the  fall  to  reach  the  upper 
part  of  the  stream.  Numerous  cases  of  this  kind  are 
known  in  the  Rocky  Mountains  and  Sierra  Nevada,  where 
a  stream  may  be  well  supplied  with  trout  below  a  fall, 
and  quite  bare  of  these  fish  above  the  fall.  In  the 
Yosemite  Valley  in  California  trout  live  in  the  Merced 
River  below  the  great  Vernal  and  Nevada  falls,  but  above 
these  falls  the  Merced  contains  no  trout.  To  fresh-water 
swimming  animals  salt  water  may  be  a  barrier;  thus  some 
kinds  of  fresh- water  fishes  are  limited  to  one  of  two 
near-by  streams  although  the  mouths  of  these  streams 
empty  near  each  other  into  the  ocean.  The  amphibious 
batrachians,  at  home  in  fresh  water  and  on  land,  are 
killed  by  contact  with  sea-water.  Earthworms  also  are 
killed  by  salt  water.  Thus  the  narrowest  ocean  strait  is 


THE  DISTRIBUTION  OF  ANIMALS  439 

as  effective  a  barrier  to  these  animals  as  a  whole  sea. 
High  mountain  ranges  and  broad  deserts  are  barriers  to 
many  land-animals,  partly  because  of  the  physical  ob- 
stacles, partly  because  of  the  differences  in  temperature 
and  in  food-supply. 

Temperature  and  climate  (as  distinct  from  temperature) 
and  the  ocean  are  the  three  great  barriers  when  we  con- 
sider the  animal  kingdom  as  a  whole,  and  look  for  the 
causes  which  determine  the  chief  zoogeographical  divisions 
of  the  earth's  surface.  Most  of  the  tropical  animals 
cannot  endure  frost,  hence  the  isothermal  line  of  frost  is 
a  line  across  which  few  tropical  animals  venture.  Most 
arctic  animals  are  enfeebled  by  heat,  and  the  isothermal 
line  which  marks  off  the  region  in  which  frost  occurs  the 
year  round  is  another  great  zoogeographical  boundary. 
But  while  these  lines  are  limits  for  localized  species,  some 
animals,  as  birds,  especially,  keep  within  a  relatively 
uniform  temperature  by  migrations  across  these  lines.  It 
should  be  borne  in  mind  that  the  gradual  decrease  in 
temperature  met  with  in  going  north  or  south  from  the 
tropics  is  also  met  in  the  ascent  of  high  mountains.  The 
summits  of  lofty  peaks,  even  in  the  tropics,  are  truly 
arctic  in  character;  they  are  snow-covered,  and  the 
animals  and  plants  on  them  are  truly  arctic.  Thus  in  the 
ascent  of  a  single  mountain  a  whole  series  of  life-zones 
from  tropical  to  arctic  can  be  traversed. 

Climate,  as  distinct  from  temperature,  establishes  limits 
of  distribution.  The  animals  of  Eastern  North  America 
accustomed  to  a  humid  atmosphere  cannot  live  in  the  dry 
plains  and  deserts  of  the  West.  Closely  associated  with 
climate  is  the  nature  of  the  plant-growth  covering  the 
land ;  here  are  forests  and  luxuriant  meadows,  there  are 
sparse  tough  grasses  of  the  dry  plateau.  The  limits  of  a 
special  kind  of  plant-growth  often  are  the  limits  of  distri- 
bution of  certain  animals. 


440  ELEMENTARY  ZOOLOGY 

The  third  great  barrier,  the  ocean,  is  perhaps  the  most 
obvious  of  all  in  its  influence.  It  is  only  in  rare  cases 
that  any  land-animal  can  independently  cross  a  great 
ocean.  Thus  the  land-animals  of  Australia  differ  from 
those  of  all  other  countries,  and  those  of  Africa  and  South 
America  have  developed  almost  independently  of  one 
another.  The  ocean  is,  as  already  mentioned,  also  a 
barrier  for  fresh-water  aquatic  animals,  arid  even  marine 
fishes  which  live  normally  in  shallow  waters  along  the 
shore  rarely  venture  across  the  great  depths  of  mid-ocean. 

The  obstacles  or  barriers  met  with  determine  the  limits 
of  a  species.  Each  species  broadens  its  range  as  far  as  it 
can.  It  attempts  unwittingly,  through  natural  processes 
of  increase,  to  overcome  the  obstacles  of  ocean  or  river, 
of  mountain  or  plain,  of  woodland  or  prairie  or  desert,  of 
cold  or  heat,  of  lack  of  food  or  abundance  of  enemies — 
whatever  the  barriers  may  be.  The  degree  of  hindrance 
offered  by  any  barrier  differs  with  the  nature  of  the  animal 
trying  to  pass  it.  That  which  forms  an  impassable 
obstacle  to  one  species  may  be  a  great  aid  to  the  spread 
of  another.  '  *  The  river  which  blocks  the  monkey  or  the 
cat  is  the  highway  of  the  fish  and  turtle.  The  waterfall 
which  limits  the  ascent  of  the  trout  is  the  chosen  home  of 
the  ouzel." 

Faunae  and  zoogeographic  areas. — The  term  fauna  is 
applied  to  the  animals  of  any  region  considered  collect- 
ively. Thus  the  fauna  of  Illinois  includes  the  entire  list 
of  animals  found  naturally  in  that  State.  The  fauna  of  a 
schoolyard  comprises  all  the  animals  found  living  naturally 
in  the  yard.  The  fauna  of  a  pond  includes  all  the  animal 
inhabitants  of  the  pond.  (Flora  is  used  similarly  of  all 
the  plants  in  a  given  region.)  The  relation  of  one  fauna 
to  another  depends  on  the  character  and  effectiveness  of 
the  barriers  between,  and  the  physical  character  of  the 
two  regions.  Thus  the  fauna  of  Illinois  differs  but  little 


'  .  '-.  THE  DISTRIBUTION  OF  ANIMALS  441 

from  that  of  Indiana  or  Iowa,  because  there  are  no  barriers 
between  the  States,  and  they  are  alike  physically.  On 
the  other  hand  the  fauna  of  California  differs  much  from 
that  of  the  Eastern  States  because  of  the  great  barriers 
(the  desert  and  the  Sierra  Nevada  Mountains)  which  lie 
between  it  and  these  States,  and  because  of  the  great 
differences  in  the  physical  and  climatic  conditions  of  the 
two  regions. 

The  land-surface  of  the  earth  has  been  divided  by 
zoogeographers  into  seven  great  realms  of  animal  life, 
based  on  the  distributional  characters  shown  by  these 
various  regions.  These  realms  are  separated  by  barriers 
of  which  the  chief  are  the  presence  of  the  sea  and  the 
occurrence  of  frost.  These  realms  are  named,  from  their 
geographical  region,  the  Arctic,  the  North  Temperate, 
the  South  American,  the  Indo- African,  the  Madagascar, 
the  Patagonian,  and  the  Australian.  Of  these  the 
Australian  alone  is  sharply  defined.  Most  of  the  others 
are  surrounded  by  a  broad  fringe  of  debatable  ground 
that  forms  a  transition  to  some  other  zone. 

Habitat  and  species. — The  habitat  of  a  species  of 
animal  is  the  region  in  which  it  is  found  in  a  state  of 
nature.  It  is  currently  believed  that  the  habitat  of  any 
animal  is  the  whole  of  that  region  for  which  it  is  best 
adapted.  But  this  is  not  necessarily  true.  In  fact  in 
most  cases  it  is  not  true.  The  trout  naturally  debarred 
from  the  rivers  in  Yellowstone  Park  by  the  waterfalls 
could  live  there  well  if  the  barrier  could  be  passed.  In 
the  case  of  one  stream  it  has  been  passed  and  the  trout 
flourish  above  the  fall.  The  success  of  the  black  and 
brown  rats  and  the  English  sparrow  in  America,  of  the 
rabbit  in  Australia,  of  bumblebees  and  house-flies  in  New 
Zealand,  all  of  which  animals  had  a  natural  habitat  not 
including  these  regions,  but  by  artificial  means  have  been 
carried  over  the  barriers  and  into  die  new  territory,  prove 


442  ELEMENTARY  ZOOLOGY 

that  "habitat"  is  not  necessarily  coincident  with  "only 
fit  region."  Shad,  striped  bass,  and  catfish  from  the 
Potomac  River  have  been  introduced  into  and  now  thrive 
in  the  Sacramento  River  in  California.  In  fact  the  whole 
work  of  the  introduction  and  diffusion  of  valuable  food- 
animals  in  territory  not  naturally  included  in  the  habitat 
of  the  species  is  based  on  our  knowledge  that  the  habitat 
of  a  species  is  often  determined  by  physical  barriers  rather 
than  by  exclusive  fitness  of  environment.  Within  the 
natural  habitat  the  environment  is  fit  for  the  species' 
existence,  outside  of  it  the  environment  may  be  fit. 

But  there  occur  numerous  instances  where  a  species 
successful  in  leaving  its  orignal  habitat  is  unsuccessful  in 
attempting  to  maintain  itself  on  new  ground.  Man  has 
introduced  various  animals  from  one  country  to  another. 
The  English  sparrow  (naturally  debarred  from  this  country 
by  the  ocean  barrier),  brought  to  America  from  Europe, 
has  covered  its  new  territory  rapidly  and  maintains  itself 
with  brilliant  success.  But  the  nightingale,  the  starling 
and  skylark  which  have  been  repeatedly  introduced  and 
set  free  are  unable  to  maintain  themselves  here. 

Species-extinguishing  and  species-forming. — Accom- 
panying the  constant  slow  migrating  of  species  into  new 
habitats  and  the  constant  slow  changing  of  environment 
and  conditions  everywhere  is  to  be  seen  a  constant  modi- 
fication of  the  fauna  of  any  region  due  to  the  inability  of 
some  species  to  maintain  their  ground,  the  predominating 
increase  of  others,  and  the  modifying  or  adaptive  chang- 
ing of  others  into  new  forms.  In  1544  the  black  rat  of 
Europe  was  introduced  into  America  and  it  soon  crowded 
out  the  native  rats,  being  in  its  turn  crowded  out  by  the 
European  brown  rat  (the  present  common  rat  in  buildings), 
introduced  about  1775.  Here  we  have  the  original  native 
species  unable  to  maintain  itself  in  competition  with  in- 
troduced forms. 


THE  DISTRIBUTION  OF  ANIMALS  443 

With  a  change  of  environing  conditions,  certain  species 
are  unable  to  maintain  themselves.  With  the  destruction 
of  the  forests  going  on  in  parts  of  our  country  the  great 
host  of  wood-creatures,  the  bears,  squirrels,  the  wood- 
birds  and  insects,  can  no  longer  maintain  themselves,  and 
grow  rare  and  disappear.  Man  often  also  influences  the 
status  of  a  species  by  checking  its  increase  either  by 
actual  slaughter,  as  with  the  bison  and  passenger-pigeon, 
or  by  making  adverse  changes  in  its  environment,  as  by 
destroying  forests,  or  putting  the  plains  under  cultivation. 

In  the  discussion  of  "  species-forming  "  (see  p.  408)  it 
was  shown  that  adaptation  may  lead  to  the  altering  of 
species,  and  to  the  formation  of  new  ones  (under  the  in- 
fluence of  natural  selection).  With  the  gradual  change  of 
conditions,  or  with  the  facing  of  new  conditions  because 
of  an  unusual  migration  to  or  invasion  of  new  territory, 
those  individuals  of  the  species  exposed  to  the  new  con- 
ditions must  adapt  themselves  in  structure  and  habit  in 
order  to  meet  successfully  the  new  demands.  By  the 
cumulative  action  of  natural  selection  these  adaptive 
changes  are  emphasized ;  and  this  emphasis  may  come  to 
be  so  pronounced  that  the  part  of  the  species  represented 
in  this  newly  acquired  territory,  if  isolated  from  the  orig- 
inal stock,  is  so  altered  as  to  be  quite  distinct  in  appear- 
ance from  the  old.  If  these  changed  individuals  are  also 
physiologically  distinct  from  the  old  stock,  i.e.  are 
unable  to  mate  with  them,  a  new  species  is  established. 
As  already  mentioned,  the  peopling  of  islands  from  main- 
lands is  an  excellent  and  readily  observable  example  of 
the  phenomena  referred  to  in  the  third  law  of  distribution. 


APPENDICES 
EQUIPMENT  AND  METHODS 


APPENDIX  I 

EQUIPMENT    AND    NOTES   OF    PUPILS 

Equipment  of  pupils. — Each  pupil  should  have  a 
laboratory  note-book  of  about  8  X  10  inches,  opening  at 
the  end,  in  which  both  drawings  and  notes  can  be  made. 
The  paper  should  be  unruled  and  of  good  quality  (not  too  • 
soft).  Each  pupil  should  have  also  instruments  of  his 
own  as  follows:  scalpel,  pair  of  small  scissors,  spring 
forceps,  pair  of  dissecting-needles,  small  glass  pipette,  and 
paper  of  ribbon-pins  for  pinning  out  specimens.  The  cost 
of  this  outfit  need  not  exceed  $1.00.  The  laboratory 
should  furnish  him  with  a  dissecting-dish  and  a  dissecting- 
microscope,  or  at  least  a  lens. 

Laboratory  drawings  and  notes. — Each  pupil  should 
make  the  drawings  called  for  in  the  directions  for  the 
laboratory  exercises.  These  drawings  should  be  in  out- 
line, and  put  in  by  pencil ;  the  lines  may  be  inked  over  if 
preferred.  Shading  should  be  used  sparingly,  if  at  all. 
Each  drawing  and  all  the  organs  and  animal  parts  repre- 
sented in  it  should  be  fully  named.  See  the  anatomical 
plates  in  this  book  for  example.  With  such  complete 
"labelling,"  little  note-taking  need  be  done  in  connec- 
tion with  the  dissections. 

Notes  should  be  made  of  any  observations  which  cannot 
be  represented  in  the  drawings;  for  example,  on  the 

447 


448  APPENDIX 

behavior  of  the  living  animals.      All  notes  referring  to 
matters  of  life-history  should  be  dated. 

Field-observations  and  notes. — Scattered  through  this 
book  will  be  found  numerous  suggestions  for  student  field- 
work,  for  the  observation  of  the  life-history  and  habits  and 
conditions  of  animals  in  nature.  As  explained  in  the 
Preface,  the  initiation  and  direction  of  such  work  must 
be  left  to  the  teacher.  But  its  importance  both  because 
of  its  instructiveness  and  its  interest  is  great.  Pupils 
should  not  only  be  incited  to  make  individual  observations 
whenever  and  wherever  they  can,  but  the  teacher  should 
make  little  field-excursions  with  the  class  or  with  parts  of 
it  at  various  times,  to  ponds  or  streams  or  woods,  and 
1 '  show  things"  to  all.  The  life-history  and  feeding- 
habits  of  insects,  the  web-making  of  spiders,  the  flight, 
songs,  nesting,  and  care  of  young  of  birds,  the  haunts  of 
fishes,  the  development  of  frogs,  toads,  and  salamanders, 
the  home-building  and  feeding-habits  of  squirrels,  mice, 
and  other  familiar  mammals  are  all  (as  has  been  called 
attention  to  at  proper  places  in  the  book)  specially  fit 
subjects  for  field-observation. 

Each  pupil  should  keep  a  field  note-book,  recording 
from  day  to  day,  under  exact  date,  any  observations  he 
may  make.  Let  the  most  trivial  things  be  noted ;  when 
referred  to  later  in  connection  with  other  notes  they  may 
not  seem  so  trivial.  The  field  note-book  should  be 
smaller  than  the  laboratory  note-  and  drawing-book, 
small  enough  to  be  carried  in  the  pocket.  Notes  should 
be  made  on  the  spot  of  observation ;  do  not  wait  to  get 
home.  Sketches,  even  rough  ones,  may  be  advanta- 
geously put  into  the  book.  Students  with  photographic 
cameras  can  do  some  very  interesting  and  valuable  field- 
work  in  making  photographs  of  animals,  their  nests  and 
favorite  haunts.  Such  photographic  work  is  very  effectively 
used  now  in  the  illustration  of  books  about  animals  and 


EQUIPMENT  AND  NOTES  OF  PUPILS 


449 


plants  (see  the  reproductions  of  photographs  in  this  book). 
If  the  class  is  making  a  collection  the  collecting  notes  or 
data  made  in  the  field-books  of  the  different  pupil  collec- 
tors should  all  be  transferred  to  a  common  "Notes  on 
Collections  ' '  book  kept  by  the  whole  class. 


APPENDIX  II 

LABORATORY    EQUIPMENT   AND    METHODS 

Equipment  of  laboratory. — The  equipment  of  the 
laboratory  or  classroom  will,  of  necessity,  depend  upon  the 
opportunities  afforded  the  teacher  by  the  school  officers  to 
provide  such  facilities  as  instruments,  books,  and  charts. 
If  dissections  are  to  be  seriously  and  properly  made, 
however,  some  equipment  is  indispensable.  Flat-topped 
tables,  not  over  30  inches  high,  a  few  compound  micro- 
scopes (one  is  much  better  than  none),  as  many  simple 
lenses,  or,  far  better,  simple  dissecting-microscopes,  as 
there  are  students,  dissecting-dishes,  a  pair  of  bone- 
clippers,  one  injecting-syringe,  a  bunch  of  bristles,  water, 
a  few  simple  reagents  and  some  inexpensive  glassware, 
as  slides,  cover-glasses,  watch-crystals,  and  fruit-  or 
battery-jars  for  live  cages  and  aquaria,  make  up  a  suffi- 
cient equipment  for  good  work.  Much  can  be  done  with 
less,  and  perhaps  a  little  more  with  some  additional 
facilities. 

The  dissecting-pans  should  be  of  galvanized  iron  or  tin, 
oblong,  about  6x8  inches  by  2  inches  deep,  with 
slightly  flaring  sides.  If  an  iron  wire  be  run  around  the 
margin,  and  the  margin  bent  back  over  it,  it  will 
strengthen  the  dish,  and  make  a  broader  and  smoother 
edge  for  the  hands  to  rest  on.  Diagonally  across  the 
dish,  about  one-fourth  inch  from  the  bottom,  should  run  a 
thick  wire.  A  layer  of  paraffin  one-half  inch  thick 


LABORATORY  EQUIPMENT  AND  METHODS  45 J 

should  cover  the  bottom.  It  should  be  poured  in  melted, 
when  the  diagonal  wire  will  be  imbedded  in  it  and  will 
hold  it  in  place.  Acids  must  not  be  put  into  the  pan. 

The  reagents  necessary  are  alcohol  of  95  per  cent  and 
85  per  cent,  and  formalin  of  4  per  cent  (the  formaldehyde 
sold  by  druggists  is  40  per  cent  and  should  be  diluted  ten 
times  with  water),  these  for  preserving  material  for  dis- 
section ;  chloroform  for  killing  specimens ;  glycerin  for 
making  temporary  microscopic  mounts,  and  20  per  cent 
nitric  acid  for  preparing  specimens  for  study  of  the  nervous 
system.  In  addition  there  will  be  needed  the  few  other 
materials  mentioned  in  the  following  paragraphs  as  neces- 
sary in  the  preparation  of  injecting-fluids,  the  staining  of 
fresh  tissue  and  preserving  by  special  methods. 

A  list  of  reference  books  desirable  in  the  laboratory  is 
appended  as  a  separate  paragraph  (see  p.  454). 

Collecting  and  preparing  material  for  use  in  the 
laboratory. — As  directions  have  been  given  in  the  "  tech- 
nical notes  ' '  scattered  through  the  book  for  the  collecting 
and  preparing  of  all  the  various  kinds  of  animals  chosen 
as  subjects  of  the  laboratory  exercises,  it  will  only  be 
necessary  to  give  here  directions  for  making  certain 
special  mixtures  and  for  the  special  preparation  of  speci- 
mens by  injection,  etc.  Specimens  to  be  used  for  dissec- 
tion should  be  kept  in  alcohol  of  85  per  cent  or  in  formalin 
of  4  per  cent.  Alcohol  is  better  for  the  earthworm,  but 
for  the  other  examples  formalin  is  either  better  or  as  good, 
and  as  it  is  much  cheaper  it  may  well  be  chosen  for  the 
general  preservative. 

Methyl  green,  a  stain  used  for  coloring  fresh  tissues. 
Dissolve  the  methyl  green  powder  in  water,  using  about 
as  much  powder  as  the  water  will  take  up.  Add  a  few 
drops  of  acetic  acid. 

Injecting-masses. — Injections  are  best  made  with  prep- 
arations of  French  gelatine,  but  white  glue  will  answer 


45  2  APPENDIX  II 

most  purposes.  For  fine  injection  use  a  combination  of 
the  following:  I  part  of  a  solution  of  gelatine,  I  part  to 
4  parts  of  water;  I  part  of  a  saturated  solution  of  lead 
acetate  in  water,  and  I  part  of  a  saturated  solution  of 
potassium  bichromate  in  water.  A  mixture  of  these  when 
hot  gives  a  beautiful  yellow  injection-mass  which,  filtered, 
will  pass  through  the  finest  capillaries.  For  different 
colorings  use  dry  paints,  which  come  in  ultramarine  blue, 
vermilion,  and  green.  The  gelatine  should  be  thoroughly 
soaked  before  the  coloring-matter  is  added.  A  mistake 
is  generally  made  in  using  the  injection-mass  too  thick. 
One  part  by  weight  of  gelatine  to  six  or  even  more  parts 
of  water  is  a  good  proportion.  The  gelatine  as  well  as 
glue-masses  should  be  made  in  a  water-bath,  which  con- 
sists of  one  dish  placed  within  another  outer  one  contain- 
ing warm  water.  The  mass  should  be  injected  warm,  not 
hot,  after  which  the  injected  specimen  is  to  be  placed  in 
cold  water  until  the  injecting-mass  has  set.  Glue  (the 
ordinary  white  kind)  can  be  used  for  most  injections  just 
as  the  gelatine  was  used,  but  should  not  be  so  much 
diluted.  All  injection-masses  should  be  filtered  through 
a  cloth  before  using. 

Preparing  skeletons — In  general,  skeletons  are  best 
cleaned  by  boiling.  After  most  of  the  flesh  has  been  cut 
away  the  skeleton  should  be  boiled  in  a  soap  solution 
until  the  remaining  parts  of  the  muscles  are  thoroughly 
softened.  The  soap  solution  is  made  of  2,000  c.c.  of 
water,  preferably  distilled,  12  grams  of  saltpetre,  and  75 
grams  of  hard  soap  (white).  Heat  these  until  dissolved, 
then  add  150  c.c.  of  strong  ammonia.  This  stock  solu- 
tion is  mixed  with  four  or  five  parts  of  water,  when  the 
mixture  is  ready  for  use.  The  bones  after  boiling  are 
rinsed  in  cold  water,  brushed  and  picked  clean,  then  left 
to  dry  on  a  clean  surface. 

Preserving  anatomical  preparations — Many  specimens 


LABORATORY  EQUIPMENT  AND  METHODS  453 

worth  keeping  will  be  found,  and  for  them  a  solution 
known  as  Fischer's  formula  is  suggested  as  good,  especially 
for  brains.  Fischer's  formula  is  made  up  as  follows: 
2,000  c.c.  of  water,  50  c.c.  of  formalin,  100  grams  of 
sodium  chloride,  and  1 5  grams  of  zinc  chloride.  These 
are  mixed  together  until  thoroughly  dissolved.  Open 
preparations  well  before  placing  them  in  the  liquid  and 
use  about  twenty  times  the  volume  of  the  object  to  be 
preserved. 

To  keep  fresh  dissections. — For  materials  which  are 
dissected  fresh  and  must  be  kept  over  for  several  days  in 
a  fresh  condition  add  a  few  drops  of  carbolic  acid  to  the 
water  which  covers  them.  Carbolized  water  (2  per  cent 
in  water)  will  preserve  a  great  many  tissues  for  a  long 
time.  Hearts  wrill  remain  for  years  in  a  supple  condition 
in  this  solution. 

Obtaining  marine  animals,  microscopic  preparations, 
etc.  —  For  schools  not  on  the  seashore  the  marine  animals 
such  as  starfishes,  etc.,  which  are  to  be  dissected  or 
examined  as  examples  of  the  branches  to  which  they 
belong  must  be  obtained  as  preserved  specimens  from 
dealers  in  such  supplies.  Among  such  dealers  on  the 
Atlantic  coast  are  the  Marine  Biological  Laboratory, 
Woods  Roll,  Mass.;  F.  W.  Walmsley,  Academy  of 
Natural  Sciences,  Philadelphia,  Pa.  ;  and  H.  H.  and  C.  S. 
Brimley,  Raleigh,  N.  C.  ;  on  the  Pacific  coast  the  Supply 
Department,  Hopkins  Seaside  Laboratory,  Stanford  Uni- 
versity, California.  Ward's  Natural  Science  Establish- 
ment, Rochester,  N.  Y.,  supplies  almost  any  biological 
specimens  asked  for.  This  establishment  furnishes  already 
made  dissections  and  sets  illustrating  life-history  and 
metamorphosis.  The  few  permanent  microscopic  prepara- 
tions which  are  mentioned  in  the  book  as  desirable  to  have 
can  be  made  by  the  teacher  if  he  has  had  any  training  in 
microscopical  technic.  If  not,  they  may  be  bought 


454  APPE NDIX  II 

cheaply  of  such  dealers  in  natural  history  supplies  as  the 
Bausch  &  Lomb  Optical  Co.,  Rochester,  N.  Y.  ;  the 
Kny-Scheerer  Co.,  17  Park  Place,  New  York  City; 
Queen  &  Co.,  1010  Chestnut  Street,  Philadelphia,  Pa., 
and  numerous  others.  From  these  dealers  also  can  be 
bought  all  of  the  laboratory  supplies,  such  as  lenses, 
slides,  cover-glasses,  dissecting-scalpels,  scissors  and 
needles,  etc.,  mentioned  in  this  book. 

Reference  books. — Throughout  the  preceding  chapters 
exact  references  have  been  made  to  various  books,  as 
many  of  which  as  possible  should  be  in  the  school-library- 
Some  of  these  references  have  been  made  with  special 
regard  to  the  teacher,  but  most  with  special  regard  to  the 
pupil.  All  of  the  books  referred  to  are  included  in  the 
following  list.  For  the  convenience  of  the  prospective 
buyer,  the  names  of  the  publishers  and  prices  of  the  books 
are  appended.  In  buying  books,  it  is  of  course  not 
necessary  to  order  from  the  various  publishers.  A  list  of 
the  books  desired  may  be  handed  to  any  book-dealer,  who 
will  order  them  and  who  should  in  most  cases  be  able  to 
get  them  for  a  little  less  than  publisher's  list  prices. 

Baskett,  J.  N.  The  Story  of  the  Birds.  1899,  D.  Appleton  &  Co.  $0.65. 
Beddard,  Frank.  Animal  Coloration.  1892,.  Macmillan  Co.  $3.50. 

—  Zoogeography.      1895,  Macmillan  Co.     #i.Co. 
Bendire,  Chas.     Directions  for  Collecting,  Preparing,  and  Preserving  Birds' 

Eggs  and  Nests.      Distributed  by  U.  S.  National  Museum. 
Bird  Lore,   an   Illustrated  Journal  about   Birds.     Macmillan  Co.    $1.00   a 

year. 
Cambridge    Natural    History,  Vols.    V  (Peripatus),   $4.00,  VI   (Insects), 

$3.56.     Macmillan  Co. 
Chapman,  Prank.     Handbook   of  the  Birds   of   Eastern   North   America. 

1899.     D.  Appleton  &  Co.     $3.00. 
Comstock,  J.  H.     Manual  for  the  Study  of  Insects.      1897,  Comstock  Pub. 

lishing  Co.     $3-75- 

Insect  Life.      1901,  D.  Appleton  &  Co.     $1.50. 

and  Kellogg,  V.  L.     Elements  of  Insect  Anatomy.      1901,  Comstock 

Publishing  Co.     #1.00. 


LABORATORY  EQUIPMENT  AND  METHODS  45i 

Cooke,  W.  W.     Bird  Migration  in  the  Mississippi  Valley.     Distributed  by 

the  Division  of  Biological  Survey,  U.  S.  Dept.  Agric. 
Cowan,  T.  W.     Natural  History  of  the  Honey-bee.     1890,  London:  Houls- 

ton.      is.  6d. 
Coues,  Elliott.     Key  to  North  American  Birds.      1890,  Estes  and  Lauriat. 

$7.50. 
Darwin,  Chas.     The  Formation  of  Vegetable  Mold  through   the  action  oi 

Worms.     D.  Appleton  &  Co.     $1.50. 

Origin  of  Species.      1896,  Caldvvell.     $0.75. 

The  Structure  and  Distribution  of  Coral  Reefs.       D.  Appleton  &  Co. 

S2.OO. 

Plants  and  Animals  under  Domestication.     D.  Appleton  &  Co. 

Davie,  Oliver.     Methods  in  the  Art  of  Taxidermy.      1894,  Oliver  Davie  & 

Co.,  Columbus,  O.     $10  net. 
Gage,  S.  H.      Life  History  of  the  Toad.     Teacher's  Leaflets  No.  9,  April, 

1898,  prepared  by  College  of  Agriculture,  Cornell  University,  Ithaca, 

N.  Y. 
Heilprin,  A.     The  Distribution  of  Animals.     1886,  D.    Appleton  &   Co. 

S2.OO. 

Hodge,  C.  F.     The  Common  Toad.     Nature  Study  Leaflet,  Biology  Series 

No.  i.  1898,  published  by  C.  H.  Hodge,  Worcester,  Mass. 
Holland,  W.  J.     The  Butterfly  Book.     1899,  Doubleday  and  McClure  Co. 

53.00. 
Hornaday,   W.  T.     Taxidermy  and    Zoological  Collecting.     1897,  Chas. 

Scribner's  Sons.     $2.50  net. 

Howell,  W.  H.     Dissection  of  the  Dog.      1889,  Henry  Holt  &  Co.     $1.00. 
Huxley,  T.  H.     The  Crayfish:  an  introduction  to  the   Study  of  Zoology. 

D.  Appleton  &  Co.     $1.75. 
Jordan,  D.  S.     Manual   of  Vertebrate  Animals  of  the    Northern  United 

States,  8th  ed.     1899,  A.  C.  McClurg  &  Co.     $2.50. 

—  and  Evermann,  B.  W.     Fishes  of  North  and  Middle  America,  4  vols. 
1898-1900,  Distributed  by  U.  S.  National  Museum. 

—  and  Kellogg,  V.  L.     Animal  Life.     1900,  D.  Appleton  &  Co.     $1.20. 
Lubbock,  John.     Ants,  Bees,  and  Wasps.     1882.  D.  Appleton  &  Co.    $2.00. 
Marshall,  H.  M.,  and  Hurst,  C.  H.     Practical  Biology,  5th  ed.    G.  P.  Put- 
nam's Sons.     $3.50. 

Martin,  H.  W.,  and  Moale,  W.  A.     Handbook  of  Vertebrate  Dissection,  3 
parts.      1881.  Macmillan  Co. 

Part   i.   How  to  dissect  a  Chelonian    (red-bellied  slider   terrapin); 
Part  2.   How  to  dissect  a  bird  (pigeon); 
Part  3.   How  to  dissect  a  rodent  (rat). 
McCook,  Henry.     American    Spiders  and    their   Spinning  Work,   3   vols. 

1889-1893,  H.  C.  McCook,  Phila.,  Pa.     $30.00. 

Miall,  L.  C.     The  Natural   History  of  Aquatic  Insects.      1895,  Macmillan 
Co.     $1.75. 


456 


APPENDIX  II 


Parker,  T.  J.     A  Course  of  Instruction  in  Zootomy.      1884,  Macmillan  Co. 

$2.25. 

Lessons  in  Elementary  Biology.      1897,  Macmillan  Co.     $2.65. 

and  Haswell,  W.  A.     Textbook  of  Zoology,  2  vols.  1897,  Macmillan 

Co.     $9.00. 
Peckham,  George  W.  and  E.  J.   On  the  Instincts  and  Habits  of  the  Solitary 

Wasps.      1898,  sold  by  Des  Forges  &  Co.,  Milwaukee,  Wis.     $2.00. 
Potts,  E.     Fresh-water  Sponges.      1887,  Phil.  Acad.  of  Sciences. 
Poulton,  E.  B.     The  Colors  of  Animals.      1890,  D.  Appleton  &  Co.    $1.75. 
Reighard,  J.  E.,  and  Jennings,  H.  S.     The  Anatomy  of  the  Cat.     1901, 

Henry  Holt  &  Co.     $4.00. 
Ridgway,   R.      Directions  for   Collecting    Birds.       Distributed    by   U.    S. 

National  Museum. 

Riverside  Natural  History,  6  vols.     Houghton,  Mifflin  &  Co.     $30.00. 
Romanes,  Geo.     Darwin  and  After  Darwin,  I.      1895-97,  Open  Court  Pub- 
lishing Co. 

Scudder,  S.  H.     The  Life  of  a  Butterfly.     1893,  Henry  Holt  &  Co.    $1.00. 
Van  Beneden,  E.     Animal  Parasites  and  Messmates.     1876,  D.  Appleton 

&  Co.     $1.50. 
Wallace,  A.  R.     The  Geographical  Distribution  of  Animals.     1876,  Harper 

&  Bros.     $10.00. 
Wallace,  A.  R.     Island  Life.      1881,  Harper  &  Bros.     $4.00. 


APPENDIX  III 

REARING   ANIMALS    AND    MAKING    COLLEC- 
TIONS 

MUCH  good  work  in  observing  the  behavior  and  life- 
history  of  some  kinds  of  animals  can  be  done  by  keeping 
them  alive  in  the  schoolroom  under  conditions  simulating 
those  to  which  they  are  exposed  in  nature.  The  growth 
and  development  of  frogs  and  toads  from  egg  to  adult,  as 
well  as  their  feeding  habits  and  general  behavior,  can  all 
be  observed  in  the  schoolroom  as  explained  in  Chapter 
XII.  Harmless  snakes  are  easily  kept  in  glass-covered 
boxes ;  snails  and  slugs  are  contented  dwellers  indoors ; 
certain  fish  live  well  in  small  aquaria,  and  many  other 
familiar  forms  can  be  kept  alive  under  observation  for  a 
longer  or  shorter  time.  But  from  the  ease  with  which 
they  are  obtained  and  cared  for,  the  inexpensiveness  of 
their  live-cages,  and  the  interesting  character  of  their  life- 
history  and  general  habits,  insects  are,  of  all  animals,  the 
ones  which  specially  commend  themselves  for  the  school- 
room menagerie.  In  the  technical  notes  in  the  chapter 
(XXI)  devoted  to  insects  are  numerous  suggestions  re- 
garding the  obtaining  and  care  of  certain  kinds  of  insects 
which  may  be  reared  and  studied  to  advantage  in  the 
schoolroom.  In  the  following  paragraphs  are  given  direc- 
tions for  making  the  necessary  live-cages  and  aquaria  for 
these  insects. 

Live-cages  and  aquaria. — Prof.  J.  H.  Comstock  has 
so  well  described  the  making  of  simple  and  inexpensive 


458  APPENDIX  III 

cages  and  aquaria  in  his  book,   "  Insect  Life,"  that,  with 
his  permission,  his  account  is  quoted  here. 

Live-cages.  —  "A  good  home-made  cage  can  be  built 
by  fitting  a  pane  of  glass  into  one  side  of  an  empty  soap- 
box.     A  board,  three  or 
four   inches  wide,  should 
be    fastened     below    the 
glass  so  as  to  admit  of  a 
layer  of  soil  being  placed 
in    the  lower  part  of  the 
cage,   and  the  glass   can 
be  made  to  slide,  so  as  to 
serve  as  a  door  (fig.  166). 
The  glass  should  fit  close- 
Fro.    166.— Soap-box    breeding-cage  for    \y   wnen    shut,   to  prevent 
insects.     (From  Jenkins  and  Kellogg.) 

the  escape  oi  the  insects. 

"In  rearing  caterpillars  and  other  leaf-eating  larvae, 
branches  of  the  food-plant  should  be  stuck  into  bottles  or 
cans  which  are  filled  with  sand  saturated  with  water.  By 
keeping  the  sand  wet  the  plants  can  be  kept  fresh  longer 
than  in  water  alone,  and  the  danger  of  the  larvae  being 
drowned  is  avoided  by  the  use  of  sand. 

"Many  larvae  when  full-grown  enter  the  ground  to 
pass  the  pupal  state ;  on  this  account  a  layer  of  loose  soil 
should  be  kept  in  the  bottom  of  a  breeding-cage.  This 
soil  should  not  be  allowed  to  become  dry,  neither  should 
it  be  soaked  with  water.  If  the  soil  is  too  dry  the  pupae 
will  not  mature,  or  if  they  do  so  the  wings  will  not  expand 
fully;  if  the  soil  is  too  damp  the  pupae  are  liable  to  be 
drowned  or  to  be  killed  by  mold. 

4 '  It  is  often  necessary  to  keep  pupae  over  winter,  for  a 
large  proportion  of  insects  pass  the  winter  in  the  pupal 
state.  Hibernating  pupae  may  be  left  in  the  breeding- 
cages  or  removed  and  packed  in  moss  in  small  boxes. 
Great  care  should  be  taken  to  keep  moist  the  soil  in  the 


REARING  ANIMALS  AND  MAKING   COLLECTIONS      459 


breeding-cages,  or  the  moss  if  that  be  used.  The  cages 
or  boxes  containing  the  pupae  should  be  stored  in  a  cool 
cellar,  or  in  an  unheated  room,  or  in  a  large  box  placed 
out  of  doors  where  the  sun  cannot  strike  it.  Low  tem- 
perature is  not  so  much  to  be 
feared  as  great  and  frequent 
changes  of  temperature. 

' '  Hibernating  pupae  can  be 
kept  in  a  warm  room  if  care  be 
taken  to  keep  them  moist,  but 
under  such  treatment  the  mature 
insects  are  apt  to  emerge  in 
midwinter. 

' '  An  excellent  breeding-cage 
is  represented  by  fig.  167.  It 
is  made  by  combining  a  flower- 
pot and  a  lantern-globe.  When 
practicable,  the  food-plant  of 
the  insects  to  be  bred  is  planted 

r  FIG.  167. —Lamp-chimney  and 

in  the  flower-pot ;  in  Other  Cases        flower-pot    breeding-cage    for 

a  bottle  or  tin  can  filled  with      £s!f s-  ,  (From  Jenkins  and 

Kellogg.) 

wet  sand  is  sunk  into  the  soil 

in  the  flower-pot,  and  the  stems  of  the  plant  are  stuck  into 
this  wet  sand.  The  top  of  the  lantern-globe  is  covered 
with  Swiss  muslin.  These  breeding-cages  are  inexpen- 
sive, and  especially  so  when  the  pots  and  globes  are 
bought  in  considerable  quantities.  A  modification  of  this 
style  of  breeding-cage  that  is  used  by  the  writer  differs 
only  in  that  large  glass  cylinders  take  the  place  of  the 
lantern-globes.  These  cylinders  were  made  especially 
for  us  by  a  manufacturer  of  glass,  and  cost  from  six  to 
eight  dollars  per  dozen,  according  to  size,  when  made  in 
lots  of  fifty. 

4<  When  the  transformation  of  small  insects  or  of  a  small 
number  of  larger  ones  are  to  be  studied,  a  convenient 


460  APPENDIX  III 

cage  can  be  made  by  combining  a  large  lamp-chimney 
with  a  small  flower-pot. 

"  The  root-cage. — For  the  study  of  insects  that  infest 
the  roots  of  plants,  the  writer  has  devised  a  special  form 
of  breeding-cage  known  as  the  root-cage.  In  its  simplest 
form  this  cage  consists  of  a  frame  holding  two  plates  of 
glass  in  a  vertical  position  and  only  a  short  distance  apart- 
The  space  between  the  plates  of  glass  is  filled  with  soil  in 
which  seeds  are  planted  or  small  plants  set.  The  width 
of  the  space  between  the  plates  of  glass  depends  on  the 
width  of  two  strips  of  wood  placed  between  them,  one  at 
each  end,  and  should  be  only  wide  enough  to  allow  the 
insects  under  observation  to  move  freely  through  the  soil. 
If  it  is  too  wide  the  insects  will  be  able  to  conceal  them- 
selves. Immediately  outside  of  each  glass  there  is  a  piece 
of  blackened  zinc  which  slips  into  grooves  in  the  ends  of 
the  cage,  and  which  can  be  easily  removed  when  it  is 
desired  to  observe  the  insects  in  the  soil. 

"Aquaria. — For  the  breeding  of  aquatic  insects  aquaria 
are  needed.  As  the  ordinary  rectangular  aquaria  are 
expensive  and  are  liable  to  leak  v/e  use  glass  vessels 
instead.  • 

"  Small  aquaria  can  be  made  of  jelly-tumblers,  glass 
finger-bowls,  and  glass  fruit-cans,  and  larger  aquaria  can 
be  obtained  of  dealers.  A  good  substitute  for  these  is 
what  is  known  as  a  battery -jar  (fig.  168).  There  are 
several  sizes  of  these,  which  can  be  obtained  of  most 
dealers  in  scientific  apparatus. 

"To  prepare  an  aquarium,  place  in  the  jar  a  layer  of 
sand ;  plant  some  water-plants  in  this  sand,  cover  the  sand 
with  a  layer  of  gravel  or  small  stones,  and  then  add  the 
required  amount  of  water  carefully,  so  as  not  to  disturb 
the  plants  or  to  roil  the  water  unduly.  The  growing 
plants  will  keep  the  water  in  good  condition  for  aquatic 
animal  life,  and  render  changing  of  the  water  unnecessary, 


REARING  ANIMALS  AND  MAKING   COLLECTIONS       461 

if  the  animals  in  it  live  naturally  in  quiet  water.  Among 
the  more  available  plants  for  use  in  aquaria  are  the  fol- 
lowing: 

"  Waterweed,  Elodea  canadensis. 

"  Bladderwort,   Utricularia  (several  species). 

44  Water -starwort,  Callitriche  (several  species). 

44  Watercress,  Nasturtium  officinale. 

44  Stoneworts,  Chara  and  Nitella  (several  species  of 
each). 

44  Frog-spittle  or  water-silk,  Spirogyra. 

44  A  small  quantity  of  duckweed,  Lcmna,  placed  on  the 
surface  of  the  water  adds  to  the  beauty  of  an  aquarium. 


FIG.  168. — Battery -jar  aquarium.     (From  Jenkins  and  Kellogg.) 


4  4  When  it  is  necessary  to  add  water  to  an  aquarium  on 
account  of  loss  by  evaporation,  rain  water  should  be  used 
to  prevent  an  undue  accumulation  of  the  mineral-water 
held  in  solution  in  other  water. ' ' 

Making  collections. — Much  is  to  be  learned  about 
animals  by  44  collecting  "  them.  But  the  collecting 


462  APPENDIX  III 

should  be  done  chiefly  with  the  idea  of  learning  about  the 
animals  rather  than  with  the  notion  of  getting  as  many 
specimens  as  possible.  To  collect,  it  is  necessary  to  find 
the  animals  alive;  one  learns  thus  their  haunts,  their  local 
distribution,  and  something  of  their  habits,  while  by  con- 
tinued work  one  comes  to  know  how  many  and  what 
different  kinds  or  species  of  each  group  being  collected 
occur  in  the  region  collected  over.  Collecting  requires 
the  sacrifice  of  life,  however,  and  this  will  always  be  kept 
well  in  mind  by  the  humane  teacher  and  pupil.  Where 
one  set  of  specimens  will  do,  no  more  should  be  collected. 
The  author  believes  that  high-school  work  in  this  line 
should  be  almost  exclusively  limited  to  the  building  up 
of  a  common  school  collection.  Let  a  single  set  of  speci- 
mens be  brought  together  by  the  combined  efforts  of  all 
the  members  of  the  class,  and  let  it  be  well  housed  and 
cared  for  permanently.  Each  succeeding  class  will  add 
to  it;  it  may  come  in  time  to  be  a  really  representative 
exhibition  of  the  local  fauna. 

The  high-school  collection  should  include  not  only 
adult  specimens  of  the  various  kinds  of  animals,  forming 
a  systematic  collection,  as  it  is  called,  but  also  all  kinds 
of  specimens  which  illustrate  the  structure  and  habits  of 
the  animals  in  question  and  which  will  constitute  a 
so-called  biological  collection.  Specimens  of  the  eggs 
and  all  immature  stages;  dissections  preserved  in  alcohol 
or  formalin  showing  the  external  and  internal  anatomy; 
nests,  cocoons,  and  all  specimens  showing  the  work  and 
industries  of  the  various  animals ;  in  short,  any  specimen 
of  the  animal  itself  in  embryonic  or  postembryonic  con- 
dition, or  any  parts  of  the  animal,  or  anything  illustrating 
what  the  animal  does  or  how  it  lives,  all  these  should  be 
collected  as  assiduously  as  the  adult  individuals.  Each 
specimen  in  the  collection  should  be  labelled  with  the 
name  of  the  animal,  the  date,  and  locality,  and  the  name 


REARING  ANIMALS  AND  MAKING   COLLECTIONS      463 


of  the  collector,  with  any  particular  information  which 
will  make  it  more  instructive.  If  such  special  data  are 
too  voluminous  for  a  label,  they  should  be  written  in  a 
general  note-book  called  "Notes  on  Collections"  (kept 
in  the  schoolroom  with  the  collection),  the  specimen  and 
corresponding  data  being  given  a  common  number  so  that 
their  association  may  be  recognized.  In  the  following 
paragraphs  are  given  brief  directions  for  catching,  pinning 
up,  and  caring  for  insects, 
for  making  skins  of  birds 
and  mammals,  and  for 
the  alcoholic  preservation 
of  other  kinds  of  animals. 
Insects. — For  catching 
insects  there  are  needed 
a  net,  a  killing-bottle,  a 
few  small  vials  of  alcohol, 
and  a  few  small  boxes  to 
carry  home  live  speci- 
mens, cocoons,  galls,  etc. 
For  preparing  and  pre- 
serving the  insects  there 
are  needed  insect-pins, 


FIG.  169. — Insect  killing-bottle;  cyanide 
of  potassium  at  bottom,  covered  with 
plaster  of  Paris.  (From  Jenkins  and 
Kellogg.) 


cork-  or  pith-lined  drawers 
or  boxes,  and  small  wide- 
mouthed  bottles  of  alco- 
hol. 

The  net,  about  2  feet  deep,  tapering  and  rounded  at 
its  lower  end,  is  made  of  cheesecloth  or  bobinet  (not 
mosquito-netting,  which  is  too  frail),  attached  to  a  ring,  one 
foot  in  diameter,  of  No.  3  galvanized  iron  wire,  which  in 
turn  is  fitted  into  a  light  wooden  or  cane  handle  about 
three  and  a  half  feet  long. 

The  killing-bottle  (fig.  169)  is  prepared  by  putting  a  few 
small  lumps  (about  a  teaspoonful)  of  cyanide  of  potassium 


4^4  APPENDIX  III 

into  the  bottom  of  a  wide-mouthed  bottle  holding  about 
four  ounces,  and  covering  this  cyanide  with  wet  plaster  of 
Paris.  When  the  plaster  sets  it  will  hold  the  cyanide  in 
place,  and  allow  the  fumes  given  off  by  its  gradual 
volatilization  to  fill  the  bottle.  Insects  dropped  into 
it  will  be  killed  in  from  two  or  three  to  ten  minutes. 
Keep  a  little  tissue  paper  in  the  bottle  to  soak  up  moisture 
and  to  prevent  the  specimens  from  rubbing.  Also  keep 
the  bottle  well  corked.  Label  it  "Poison,"  and  do  not 
breathe  the  fumes  (hydrocyanic  gas).  Insects  may  be  left 
in  it  over  night  without  injury  to  them. 

Butterflies  or  dragon-flies  too  large  to  drop  into  the 
killing-bottle  may  be  killed  by  dropping  a  little  chloro- 
form or  benzine  on  a  piece  of  cotton,  to  be  placed  in  a 
tight  box  with  them.  Larvae  (caterpillars,  grubs,  etc.) 
and  pupae  (chrysalids)  should  be  dropped  into  the  vials  of 
alcohol. 

In  collecting,  visit  flowers,  sweep  the  net  back  and 
forth  over  the  small  flowers  and  grasses  of  meadows  and 
pastures,  look  under  stones,  break  up  old  logs  and  stumps, 
poke  about  decaying  matter,  jar  and  shake  small  trees 
and  shrubs,  and  visit  ponds  and  streams.  Many  insects 
can  be  collected  in  summer  at  night  about  electric  lights, 
or  a  lamp  by  an  open  window. 

When  the  insects  are  brought  home  or  to  the  school- 
room they  must  be  "  pinned  up."  Buy  insect-pins,  long, 
slender,  small-headed,  sharp-pointed  pins,  of  a  dealer  in 
naturalists'  supplies  (see  p.  453).  These  pins  cost  ten 
cents  a  hundred.  Order  Klaeger  pins,  No.  3,  or  Carls- 
baeder  pins,  No.  5.  These  are  the  most  useful  sizes. 
For  larger  pins  order  Klaeger  No.  5  (Carlsbaeder  No.  8) ; 
for  smaller  order  Klaeger  No.  I  (Carlsbaeder  No.  2). 
Pin  each  insect  straight  down  through  the  thorax  (fig.  170) 
(except  beetles,  which  pin  through  the  right  wing-cover 
near  the  middle  of  the  body).  On  each  pin  below  the 


REARING  ANIMALS  AND  MAKING   COLLECTIONS      465 

insect  place  a  small  label  with  date  and  locality  of  capture. 
Insects  too  small  to  be  pinned  may  be  gummed  on  to 
small  slips  of  cardboard,  which  should  be  then  pinned  up. 
Keep  the  insects  in  drawers  or  boxes  lined  on  the  bottom 
with  a  thin  layer  of  cork,  or  pith  of  some  kind.  (Corn- 
pith  can  be  used;  also  in  the  West,  the  pith  of  the  flower- 
ing stalk  of  the  century  plant.)  The  cheapest  insect- 
boxes  and  very  good  ones,  too,  are  cigar-boxes.  But 


FIG.  170. — Insect  properly  "pinned  up."     (From  Jenkins  and  Kellogg.) 

unless  well  looked  after  they  let  in  tiny  live  insects  which 
feed  on  the  dead  specimens.  Fora  permanent  collection, 
therefore,  it  will  be  necessary  to  have  made  some  tight 
boxes  or  drawers.  Glass-topped  ones  are  best,  so  that 
the  specimens  may  be  examined  without  opening  them. 
A  "moth-ball  "  (naphthaline)  fastened  in  one  corner  of 
the  box  will  help  keep  out  the  marauding  insects. 

Butterflies,  dragon-flies,  and  other  larger  and  beautiful- 
winged  insects  should  be  "spread,"  that  is,  should  be 
allowed  to  dry  with  wings  expanded.  To  do  this  spread- 
ing- or  setting-boards  (figs.  171  and  172)  are  necessary. 
Such  a  board  consists  of  two  strips  of  wood  fastened  a  short 
distance  apart  so  as  to  leave  between  them  a  groove  for 
the  body  of  the  insect,  and  upon  which  the  wings  are  held 
in  position  until  the  insect  is  dry.  A  narrow  strip  of  pith 
or  cork  should  be  fastened  to  the  lower  side  of  the  two 


466 


APPENDIX  HI 


strips  of  wood,  closing  the  groove  below.  Into  this  cork 
is  thrust  the  pin  on  which  the  insect  is  mounted.  An- 
other strip  of  wood  is  fastened  to  the  lower  sides  of  the 
cleats  to  which  the  two  strips  are  nailed.  This  serves 

as  a  bottom  and  protects 
the  points  of  the  pins  which 
project  through  the  piece  of 
cork.  The  wings  are  held 
down,  after  having  been  out- 
spread with  the  hinder  mar- 
gins of  the  fore  wings  about 
at  right  angles  to  the  body, 
by  strips  of  paper  pinned 
down  over  them. 

'  *  Soft  specimens  ' '  such  as 
insect  larvae,  myriapods,  and 
spiders  should  be  preserved 
in  bottles  of  alcohol  (85  per 
cent).  Nests,  galls,  stems, 
and  leaves  partly  eaten  by 
insects,  and  other  dry  speci- 
mens can  be  kept  in  small 
pasteboard  boxes. 

For  a  good  and  full  ac- 
count of  insect-collecting  and 
preserving,  with  directions 
for  making  insect-cases,  etc. , 
see  Comstock's  "Insect 
Life,"  pp.  284-314. 

Birds.  —  In  collecting 
birds,  shooting  is  chiefly  to  be  relied  on.  Use  dust-shot 
(the  smallest  shot  made)  in  small  loads.  For  shooting 
small  birds  it  is  extremely  desirable  to  have  an  auxiliary 
barrel  of  much  smaller  bore  than  the  usual  shotgun  which 
can  be  fitted  into  one  of  the  regular  gun-barrels.  In  such 


FIG.  171. — Setting-board  with  butter- 
flies properly  "spread."  (After 
Comstock. ) 


REARING  ANIMALS  AND  MAKING   COLLECTIONS      46  7 

an  auxiliary  barrel  use  32 -calibre  shells  loaded  with  dust- 
shot  instead  of  bullets.  Plug  up  the  throat  and  vent  of 
shot  birds  with  cotton,  and  thrust  each  bird  head  down- 
ward into  a  cornucopia  of  paper.  This  will  keep  the 
feathers  unsoiled  and  smooth. 

Birds  should  be  skinned  soon  after  bringing  home,  after 
they  have  become  relaxed,  but  before  evidences  of  decom- 
position are  manifest.  The  tools  and  materials  necessary 
to  make  skins  are  scalpel,  strong  sharp-pointed  scissors, 


FiG.  172.— Setting-board  in  cross-section  to  show  construction.     (After 
Comstock.) 

bone-cutters,  forceps,  corn-meal,  a  mixture  of  two  parts 
white  arsenic  and  one  part  powdered  alum,  cotton,  and 
metric-system  measure.  Before  skinning,  the  bird  should 
be  measured.  With  a  metric-system  measure  carefully 
take  the  alar  extent,  i.e.  spread  from  tip  to  tip  of  out- 
stretched wings;  length  of  wing,  i.e.  length  from  wrist- 
joint  to  tip;  length  of  bill  in  straight  line  from  base  (on 
dorsal  aspect)  to  tip;  length  of  tarsus,  and  length  of 
middle  toe  and  claw. 

To  skin  the  bird,  cut  from  amis  to  point  of  breast-bone 
through  the  skin  only.  Work  skin  away  on  each  side  to 
legs;  push  each  leg  up,  cut  off  at  knee-joint,  skin  down 
to  next  joint,  remove  all  flesh  from  bone,  and  pull  leg 
back  into  place;  loosen  skin  at  base  of  tail,  cut  through 
vertebral  column  at  last  joint,  being  careful  not  to  cut 


468  APPENDIX  III 

through  bases  of  tail-feathers ;  work  skin  forward,  turning 
it  inside  out,  loosening  it  carefully  all  around,  without 
stretching,  to  wings;  cut  off  wings  at  elbow-joint,  skin 
down  to  next  joint  and  remove  flesh  from  wing-bones; 
push  skin  forward  to  base  of  skull,  and  if  skull  is  not  too 
large  (it  is  in  ducks,  woodpeckers,  and  some  other  birds), 
on  over  it  to  ears  and  eyes ;  be  very  careful  in  loosening 
the  membrane  of  ears  and  in  cutting  nictitating  membrane 
of  eyes ;  do  not  cut  into  eyeball ;  remove  eyeballs  without 
breaking;  cut  off  base  of  skull,  and  scoop  out  brain; 
remove  flesh  from  skull,  and  "  poison  "  the  skin  by  dust- 
ing it  thoroughly  with  the  powdered  arsenic  and  alum 
mixture.  Turn  skin  right  side  out,  and  clean  off  fresh 
blood-stains  by  soaking  them  up  with  corn-meal;  wash 
off  dried  blood  with  water,  and  dry  with  corn-meal. 
Corn-meal  may  be  used  during  skinning  to  soak  up  blood 
and  grease. 

There  remains  to  stuff  the  skin.  Fill  orbits  of  eyes  with 
cotton  (this  can  be  advantageously  done  before  skin  is 
reversed) ;  thrust  into  neck  a  moderately  compact,  elastic, 
smooth  roll  of  cotton  about  thickness  of  the  natural  neck; 
make  a  loose  oval  ball  of  size  and  general  shape  of  bird's 
body  and  put  into  body-cavity  with  anterior  end  under 
the  posterior  end  of  neck-roll ;  pull  two  edges  of  abdominal 
incision  together  over  the  cotton,  fasten,  if  necessary, 
with  a  single  stitch  of  thread,  smooth  feathers,  fold  wings 
in  natural  position,  wrap  skin,  not  tightly,  in  thin  sheet 
of  cotton  (opportunity  for  delicate  handling  here)  and  put 
away  in  a  drawer  or  box  to  dry.  Before  putting  away  tie 
label  to  leg,  giving  date  and  locality  of  capture,  sex  and 
measurements  of  bird,  and  name  of  collector.  Before 
bird  is  put  into  permanent  collection  it  should  be  labelled 
with  its  common  and  scientific  name. 

The  mounting  of  birds  in  lifelike  shape  and  attitude  is 
hard  to  do  successfully;  and  a  collection  of  mounted  birds 


REARING  ANIMALS  AND  MAKING   COLLECTIONS      469 

demands  much  more  room  and  more  expensive  cabinets 
than  one  of  skins.  For  instructions  for  the  mounting  of 
birds  see  Davie's  "  Methods  in  the  Art  of  Taxidermy," 
pp.  39-57;  or  Hornaday's  <4  Taxidermy  and  Zoological 
Collecting."  For  a  more  detailed  account  of  making 
bird-skins,  see  also  these  books,  or  Ridgway's  "  Direc- 
tions for  Collecting  Birds. ' ' 

In  collecting  birds'  nests  cut  off  the  branch  or  branches 
on  which  the  nest  is  placed  a  few  inches  above  and  below 
the  nest,  leaving  it  in  its  natural  position.  Ground-nests 
should  have  the  section  of  the  sod  on  which  they  are 
placed  taken  up  and  preserved  with  them.  If  the  inner 
lining  of  the  nest  consists  of  feathers  or  fur  put  in  a 
"  moth-ball  "  (naphthaline). 

To  preserve  birds'  eggs  they  should  be  emptied  through 
a  single  small  hole  on  one  side  by  blowing.  Prick  a 
hole  with  a  needle  and  enlarge  with  an  egg-drill  (obtain 
of  dealers  in  naturalists'  supplies,  see  p.  453.)  Blow  with 
a  simple  bent  blowpipe  with  point  smaller  than  the  hole. 
After  removing  contents  clean  by  blowing  in  a  little 
water,  and  blowing  it  out  again.  After  cleaning,  place 
the  egg,  hole  downward,  on  a  layer  of  corn-meal  to  dry. 
Label  each  egg  by  writing  on  it  near  the  hole  a  number. 
Use  a  soft  pencil  for  writing.  This  number  should  refer 
to  a  record  (book)  under  similar  number,  or  to  an  '  *  egg- 
blank,"  containing  the  following  data:  name  of  bird, 
number  of  eggs  in  set,  date  and  locality,  name  of  col- 
lector, and  any  special  information  about  the  eggs  or  nest 
which  the  collector  may  think  advisable.  The  eggs  may 
be  kept  in  drawers  or  boxes  lined  with  cotton,  and  di- 
vided into  little  compartments. 

For  detailed  directions  for  collecting  and  preserving 
birds'  eggs  and  nests,  see  Bendire's  "  Directions  for  Col- 
lecting, Preparing,  and  Preserving  Birds'  Eggs  and 


47°  APPENDIX  III 

Nests  "  or  Davie's  "  Methods  in  the  Art  of  Taxidermy, " 
pp.  74-78- 

*  Mammals. — Any  mammal  intended    for  a    scientific 
specimen  should  be  measured  in  the  flesh,  before  skinning, 
and  as  soon  after  death  as  practicable,  when  the  muscles 
are    still    flexible.        (This    is  particularly  true  of   larger 
species,   such    as  foxes,    wildcats,    etc.)       The   measure- 
ments are  taken  in  millimetres,  a  rule  or  steel  tape  being 
used,      (i)   Total  length:   stretch  the  animal  on  its  back 
along  the  rule  or  tape  and  measure   from  the  tip  of  the 
nose  (head  extended  as  far  as  possible)  to  the  tip  of  the 
fleshy  part  of  tail  (not  to  end  of  hairs).      (2)   Tail:  bend 
tail  at  right  angles  from  body  backward  and  place  end  of 
ruler  in  the  angle,  holding  the  tail  taut  against  the  ruler. 
Measure  only  to  tip  of  flesh  (make  this  measurement  with 
a  pair  of  dividers).      (3)   Hind  foot:   place  sole  of  foot  flat 
on  ruler  and  measure  from  heel  to  tip  of  longest  toe-nail 
(in  certain  small  mammals  it  is  necessary  to  use  dividers 
for  accuracy).      The  measurements  should  be  entered  on 
the  label,  along  with  such  necessary  data  as  sex,  locality, 
date,  and  collector's  name. 

Skin  a  mammal  as  soon  after  death  as  possible.  Lay 
mammal  on  back  and  with  scissors  or  scalpel  open  the 
skin  along  belly  from  about  midway  between  fore  and  hind 
legs  to  vent,  taking  care  not  to  cut  muscles  of  abdomen. 
Skin  down  on  either  side  of  the  body  by  working  the  skin 
from  flesh  with  fingers  till  hind  legs  appear.  Use  corn- 
meal  to  stanch  blood  or  moisture.  With  left  hand  grasp 
a  leg  and  work  the  knee  from  without  into  the  opening 
just  made;  cut  the  bone  at  the  knee,  skin  leg  to  heel  and 
clean  meat  off  the  bone  (leaving  it  attached  of  course  to 
foot).  In  animals  larger  than  squirrels  skin  down  to  tips 

*  The  following  directions  for  making  skins  of  mammals  were  written 
for  this  book  by  Mr.  W.  K.  Fisher  of  Stanford  University,  an  experienced 
collector. 


REARING  ANIMALS  AND  MAKING   COLLECTIONS      471 

of  toes.  Do  the  same  with  other  leg.  Skin  around  base 
of  tail  till  the  skin  is  free  all  around  so  that  a  grip  can  be 
secured  on  body;  then  with  thumb  and  forefinger  hold  the 
skin  tight  at  base  of  tail  and  slowly  pull  out  the  tail.  In 
small  mammals  this  can  be  done  readily,  but  in  foxes  it 
is  often  necessary  to  split  the  skin  up  along  the  under  side 
and  dissect  it  off  the  tail-bones.  After  the  tail  is  free 
?,kin  down  the  body,  using  the  fingers  (except  in  large 
mammals)  till  the  fore  legs  are  reached;  treat  the  fore  legs 
i.i  the  same  manner  as  hind  legs,  thrusting  elbow  out  of 
the  skin  much  as  a  person  would  do  in  taking  off  a  coat; 
cut  bone  at  elbow;  clean  fore-arm  bone.  Skin  over  neck 
to  base  of  ears.  With  scalpel  cut  through  ears  close  to 
skull.  With  scalpel  dissect  off  skin  over  the  head  (taking 
care  not  to  injure  eyelids)  down  to  tip  of  nose,  severing 
its  cartilage  and  hence  freeing  skin  from  body.  Sew 
mouth  by  passing  needle  through  under  lip  and  then  across 
through  two  sides  of  the  upper  lip;  draw  taut  and  tie 
thread.  Poison  skin  thoroughly.  Turn  skin  right  side 
out.  Next  sever  the  skull  carefully  from  body,  just  where 
the  last  neck-vertebra  joins  the  back  of  the  skull.  It  is 
necessary  to  keep  the  skull,  because  characters  of  bone  and 
teeth  are  much  used  in  classification.  Remove  superfluous 
meat  from  the  skull  and  take  out  brain  with  a  little  spoon 
made  of  a  piece  of  wire  with  loop  at  end.  Tag  the  skull 
with  a  number  corresponding  to  that  on  skin,  and  hang 
up  to  dry.  A  finished  specimen  skull  is  made  by  boiling 
it  a  short  time  and  picking  the  meat  off  with  forceps, 
further  cleaning  it  with  an  old  tooth-brush,  when  it  is 
placed  in  the  sun  to  bleach.  Care  must  be  taken  always 
not  to  injure  bones  or  dislodge  teeth. 

Mammals  are  stuffed  with  cotton  or  tow;  the  latter  is 
used  in  species  from  a  gray  squirrel  up.  Large  mammals 
stuffed  with  cotton  do  not  dry  readily,  and  often  spoil. 
Being  much  thicker-skinned  than  birds,  mammals  require 


47 2  APPENDIX  III 

more  care  in  drying  and  ordinarily  require  a  much  longer 
period.  Soft  hay  may  be  substituted  for  tow;  never  use 
feathers  or  hair.  Roll  a  longish  wad  of  cotton  about  the 
size  of  body  and  insert  with  forceps,  taking  care  to  form 
the  head  nearly  as  in  life.  Split  the  back  end  of  the  cot- 
ton and  stuff  each  hind  leg  with  the  two  branches  thus 
formed.  Roll  a  piece  of  cotton  around  end  of  forceps 
and  stuff  fore  legs.  Place  a  stout  straight  piece  of  wire 
in  the  tail,  wrapping  it  slightly  to  give  the  tail  the  plump 
appearance  of  life.  (If  the  cotton  cannot  be  reeled  on  to 
the  wire  evenly,  leave  it  off  entirely.)  Make  the  wire 
long  enough  to  extend  half  way  up  belly.  Sew  up  slit  in 
belly.  Lay  mammal  on  belly  and  pin  out  on  a  board 
by  legs,  with  the  fore  legs  close  beside  head,  and  hind 
legs  parallel  behind,  soles  downward.  Be  sure  the  label 
is  tied  securely  on  right  hind  leg. 

For  directions  for  preparing  and  mounting  skeletons  of 
birds,  mammals,  and  other  vertebrates,  see  the  books  of 
Davie  and  Hornaday  already  referred  to. 

FisJies,  batrachians,  reptiles,  and  oilier  animals. — The 
most  convenient  and  usual  way  of  preserving  the  other 
vertebrates  (not  birds  or  mammals)  is  to  put  the  whole 
body  into  85  per  cent  alcohol  or  4  per  cent  formalin. 
Batrachians  should  be  kept  in  alcohol  not  exceeding  60 
per  cent  strength.  Several  incisions  should  always  be 
made  in  the  body,  at  least  one  of  which  should  penetrate 
the  abdominal  cavity.  Anatomical  preparations  are  simi- 
larly preserved.  By  keeping  the  specimens  in  glass  jars 
they  may  be  examined  without  removal.  Fishes  should 
not  be  kept  in  formalin  more  than  a  few  months,  as  they 
absorb  water,  swell,  and  grow  fragile. 

Of  the  invertebrates  all,  except  the  insects,  are  pre- 
served in  alcohol  or  formalin.  The  shells  of  molluscs 
can  be  preserved  dry,  of  course,  in  drawers  or  boxes 
divided  into  small  compartments. 


INDEX 


Illustrations  are  indicated  by  ar,  asterisk 


Acanthia  lectnlaria,  *i88. 

Acarina.  230. 

AiHiara  spectorntn,  *248. 

Actinozoa,  97,  102. 

Adaptation,  407. 

Adder,  spreading,  321. 

sEgialitis  vocifcra,  349. 

Agalenidae,  235. 

Avkistrodon  piscivorous.  323. 

Aix  sponsa,  347. 

Albatross,  346. 

A  lea  impennis,  345. 

Alee  americana,  *$%$,  396. 

Alligator,  326. 

Alligator  mississippensis,  316. 

Alternation  of  generations,  96. 

Ambfaplites  rupestris,  282. 

Amblysloma,  297,  298. 

Amblystoma  macnlatutn,  299. 

Amenirus.  282. 

Amoeba,   *32;  structure    and  life  of, 

31- 

Atnphiojcns,  278. 

Anaconda,  324. 

Anas  boschas.  347. 

Anatomy  defined,  3. 

Anguilla,  284. 

Angmliula,  140. 

A  noli  s  princtpalis,  319. 

Anosia  plexippus,  anatomy  of  larva 
of,  177,  external  structure  of.  171, 
*I72;  life  of.  175;  mimicked  by 
Basilarchia  archippus,  *433- 

Anseres,  347. 

Ant,  little  black,  *224;  little  brown, 
223. 

Antelope,  *395,  396. 

Antenna  of  carrion  beetle,  *i84- 

Antilocapra  anieriiana,  *395-  396. 

Antrostomns  vociftrtts,  356. 


i  Ant,  212,  218,  223. 
Anura,  299. 
Ape,  401. 
Aphidiae,  200. 
Apis  florea,  comb  ot,  *222. 
Apis  nielli  fie  a,  *2l8. 
Appearance,  terrifying,  430. 
Aquarium,  457. 
Aquarium,  battery-jar,  *46i, 
Aquila  chrysidos.  342. 
Arachnida,  144.  229. 
Arctomys  monax.  391. 
Ardea  hero di as,  358. 
Ardea  virescens,  347. 
Argiope  sp.,  *236. 
Argonaut,  257. 
Argonauta  argo,  257. 
Arioliinax  californica,  *2$2. 
Arthogastra,  230. 
Arthropoda,  144. 
Ascidian,  259,  *26i. 
Aspidiotus  aurantii,  *I98. 
Asterias  sp.,   structure    and  life  of, 

108. 

Asterias,     *IO9  ;     cross  -  section    of, 
*II2. 

Asterias  ocracia,  *I22. 

Aster ina  mineata,  *I22. 

Asteroidea,  120.  121, 

Attidne.  235. 

Auk,  great,  345. 

Aves.  327. 

^Avthya  vallisneria,  347- 
'Ayu,  283. 

Back-swimmer,  197.  199. 
Balanus,  *i53. 
Balana  gladalis,  393. 
Balccna  mysticetus,  393, 
JJarbadoes  earth,  82. 

473 


474 


INDEX 


Barnacle,  *I53,  155;  sessile,  155; 
stalked,  155. 

Barn-owl,  353. 

Bartramia  longicauda,  349. 

Bascanium  constrictor,  321. 

Bass,  282. 

Bat,  hoary,  *3Q2. 

Batrachia,  291. 

Batrachians,  291;  body  form  and 
structure  of,  292;  classification  of, 
295;  life-history  and  habits  of, 
295 ;  structure  of,  292. 

Bat,  39.1. 

Bead-snake,  322. 

Bear,  398. 

Beaver,  391. 

Bed-bug,  *i88. 

Bee,  212;  solitary,  216. 

Beetle,  great  water-scavenger,  163; 
external  structure,  *i6q.  ;  inter- 
nal structure,  *i6j;  antenna  of 
carrion,  *i84;  Colorado  potato. 
209. 

Beetle,  206;  carrion,  209;  whirligig, 
206. 

Bell -animalcule,    structure    and    life 

of»  75- 

Bills  of  birds,  362. 

Bipinnaria,  119. 

Bird,  frigate,  346  ;  man-of-war. 
346;  outline  of  body  showing  ex- 
ternal regions,  *33O;  ruby-throat 
humming,  nest  and  eggs  of, 

*357- 

Bird-louse,  *IQ4. 

Birds,  327;  bills  and  feet  of,  362; 
body  form  and  structure  of,  336; 
care  of  young,  366;  classification 
of,  340;  collecting,  466;  determin- 
ing, 359;  development  and  life- 
history  of,  339;  feeding  habits  of, 
370  ;  flight  and  songs  of,  364  ; 
migration  of,  367 ;  molting  of,  361 ; 
nesting  of  366;  protection  of,  370. 

Bird-skins,  making,  466. 

Bison  bison,  396,  *397- 

Bittern,  348. 

Blacksnake,  321. 

Blissus  leucopterus,  198. 

Blood,  circulation  of,  in  mammal, 
*376. 

Blood  of  toad,  structure  of,  40. 

Blow-fly,  2QI,  2O2 ;  section  through 
compound  eye  of.  *i85- 

"  Bob  Jordan"  (monkey),  "400. 


Bobwhite,  350. 

Bo  tub  us,  216. 

Bombvx  mori   anatomy  of  larva  of. 

*i78. 

Bonasa  umbellus,  350. 
Books,  reference,  454. 
Borer,  peach-tree,  *2io. 
Botaurus  lentiginosus,  348. 
Box  tortoise.  315. 
Brachynotus  nudus,  *I53- 
Brains  of  vertebrates,  ^378. 
Branch,  defined,  73. 
Branta  canadensis,  347. 
Breeding  cage,  458.  459. 
Brittle-stars,  120,  121,  122. 
Bubo  virginianus,  353. 
Buffalo,  396,  *397. 
Bufo    lentiginosus,    301 ;     dissection 

of,  5- 

Bullfrog,  299. 

Bumblebee,  216. 

Bunodes  calif  arnica,  103. 

Buteo,  353. 

Butterfly,  external  structure  of,  171, 
^172  ;  life  of,  175  ;  monarch, 
anatomy  of  larva  of,  177  ;  dead 
leaf,  *429;  mimicked  by  viceroy, 

*433- 
Butterflies,    205;    setting-board   for, 

*466,  467. 
Buzzard,  turkey,  35-. 

Cachalot,  393. 

Cage,  lamp-chimney  and  flower-pot 
breeding,  *459;  soap-box  breed- 
ing, *458. 

Cake-urchin,  124. 

Calcarea,  91. 

CallipJiora  vomit  or  ia,  202  ;  section 
through  compound  eye  of,  *i85. 

Callorhinus  alascanns,  *399- 

Callorhinus      ^^rsim^s,      parasitized, 

*422. 

Canibarus  sp.,  dissection  of,  18;  life 

of,  146. 

CampJiephilus  principalis ,  355. 
Cancer -produclus,  *I53. 
Canis  familiaris,  398. 
Ccinis  latrans,  398. 
Cams  nubilus,  398. 
Canvas -back,  347. 
Carcharcdon,  280. 
Caribou,  396. 
Cassowary,  343. 
Castor  canadensis,  391. 


INDEX 


475 


Caterpillar,    apple  tent,   208;  forest 

tent,  209. 
Catfish,  282. 
Cathartes  aura,  352. 
Cavia,  390. 
Cell,  defined,  37. 

Cell  differentiation,  degrees  of,  54. 
Cell  products,  38. 
Cell  wall,  38. 

Centiped,  *228,  229;  skein,  *228. 
Centipeds,  226. 

Centrocercus  urophasianus,  350. 
Centrums  sp.,  ^236. 
Cephalpoda,  246. 
Cercopithicus,  *4OO. 
Cervus  canadensis,  *394,  395. 
Ceryle  alcyon,  354. 
Cete,  393. 

Ceiorhinus.  270,  280. 
Chictura  pelagica,  356. 
Chain-snake,  320. 
Chalk,  81. 

Chameleon,  green.  318. 
Chelonia,  313,  314. 
Chelonia  my  das,  315. 
Chelydra  serpentina,  314. 
Chen  hyperborea,  247. 
Chicken-hawk,  353. 
Chimney-swift,  356. 
Chinch  bug,  198. 
Chipmunk,  391. 
Chiroptera,  391. 
Chitin,  145,  158. 
Chlorostouiuni  funebrale,  *248. 
Chordata,  259;  classification  of,  260. 
Chordeiies  virginianus,  356. 
Chnxmatophore,  256. 
Chub,  282. 
Chrysemys,  314. 
Cicada,    199  ;  seventeen-year,  *2OO; 

septendccim,  *2OO,    197. 
Circulation   of    blood    in    mammal, 

*37°- 

Circus  hudsonins,  352. 

Cistudo  Carolina,  314. 

Clams,  246;  hard  shell,  247;  soft- 
shell.  247. 

Class,  defined,  7^. 

Classification,  basis  and  signification 
of,  65;  defined.  3;  example  of.  68. 

Clisiocampa  americana.  larvae,  *2o8. 

Clisiocampa  dis  stria,  caterpillars, 
*209;  life-history  ot,  207. 

Cliipea  /tarengus,  284. 

Cobra-da-capcllo,  3.4. 


Coccidae,  198. 

Coccyges,  354. 

Coccyzus,  354. 

Cock,  chapparal,  354. 

Cockroach,  192. 

Codfish,  284. 

Ccecilians,  302. 

Coelenterata,  92;  classification  of, 
96  ;  development  and  life-history 
of,  95;  form  of,  93;  skeleton  of, 
95 ;  structure  of,  94. 

Colaptes  auratiis,  ""355. 

Colaptes  cafer,  355. 

Coleoptera,  206. 

Coiimis  virginianns,  350. 

Collections,  making,  461. 

Color,  use  of,  424. 

Colors,  warning.  430. 

Colubrido;,  319. 

L'oliunba  fasciata,  351. 

Lolmnba  livia,  351. 

Columbse,  351. 

Colyuibus  atiritus,  343 

Comb-building  of  honey-bee,  *22l. 

Comb   of    East   Indian     honey-bee, 

*222. 

Commensalism,  155,  413. 
Communal  life,  411. 
Condor,  California,  352. 
Condyhira  cr  is  tat  a,  391. 
Conjugation,  35,  60. 
Conotrachelus  craltcgi,  *2I2,  213. 
Conotrachelits  nenuphar,  *2\\. 
Constrictor,  boa,  324. 
Conunts  carolincnsis,  353. 
Coot,  American,  349. 
Copperhead,  322. 
Coral,     95;    branching,    *IO4;    red, 

106. 

Coral  islands,  104,  106. 
Coral  polyps,  104. 
Coral  reefs,  106. 
Corals,  92,  102,  104. 
Coregonus,  283. 
Corisa,  197. 
Corisa  sp.,  *I99. 
Cormorant,  346. 

Cornea  of  eye  of  horse-fly,   *i86. 
Cottontail.  390. 
Coyote,  398. 

Crab.  151,  152;  soft-shelled,  154. 
Crabs,  *I53- 

Crane,  sand-hill.  348;  whooping, 348. 
Crayfish,  dissection  of,  18,  *l8,   22; 

life  of,  146. 


476 

Cricket,  house,  *I93T 
Cricket,  192. 
Crinoid,  *i26. 
Crinoidea,  121,  125. 
Crocodile,  326. 
Crocodilea,  313,  325. 
Crocodilus  ainericanus,  326. 
Crotalus,  322. 
Crustacea,     144,     146  ;     for 

structure  of,    147. 
Cryptobranchns,  298. 
Ctenophora,  97,  107. 
Cuckoos,  354. 
Cucumaria,  124. 
Cucumber-beetles,  209. 
Culex  sp.,  204,  *2O5. 
Curculio  plum,  ^214. 
Curculio  quince,  *2i2,  213. 
Curlew,  long-billed,  350. 
Cuttlefishes,  255. 
Cyclas,  247. 
Cyclophis  tzstivus,  320. 
Cyclops,  148,  *I49. 
Cyclostomata,  278. 
Cytoplasm,  38. 


Dabchick,  343. 

Dactylus  sp., 

Damp  bug,  *I5I. 

Darters,  282. 

Dasyatis,  281. 

Decapoda,  151. 

Decapods,  256. 

Deer,  396. 

Degeneration.  .41 7. 

Dendrostotniuni  cronjhelmi,  *I34- 

Development,  defined,  3  ;  embry- 
onic, defined,  62;  post-embryonic, 
defined,  62;  simplest,  59. 

Diapheromera  femorata,  *427- 

Diaspis  rosa>,  ^198. 

Dictynidse,  235. 

Didelphis  virginiana,  390. 

Dieniy stylus  torosus,  *299. 

Diemy  stylus  viridescens,  297. 

Dimorphism,  96. 

Diptera,  201. 

Distribution,  barriers  to,  437;  geo- 
graphical, 435  ;  laws  of,  436  ; 
local,  of  birds.  367;  modes  of,  437. 

Diver,  great  northern,  343. 

Dolphins,  393.  • 

Doris  tuberculata,  ^254. 

Draco,  319. 

Dratr on-fl ies.   7n/i. 


INDEX 


Dragon-fly, 
Dragon,  flying,  318. 
Drawings,  447. 
Dryobates  fittbescens,  355. 
Dry  abates  villosus,  355. 
Duck,  ruddy,  347. 
Dyticus  sp.,  210. 
Dytiscidse,  207. 

Eagle,  bald,  352;  golden,  352. 

Ear  of  locust,  *i87. 

Earthworm,  anatomy  of.  *I26  ;  ali- 
mentary canal  of,  *I26  ;  cross- 
section  of,  *I3I  ;  reproductive 
organs  of,  *J-3O;  structure  and  life 
of,  127. 

Earthworms,  136. 

Echinoderm,  development  of,  119  ; 
structure  of,  117;  shape  of,  116. 

Echinodermata,  108  ;  classification 
of,  1 20. 

Echinodoris  sp.,  *254. 

Echinoidea,  121,  122,  123. 

Eciton,  225. 

Ecology,  animal,  403. 

Ectopistes  migratorius,  351. 

Eel,  284. 

Eft,  green,  297;  western  brown, 
*299. 

Eggs  of  birds,  collecting,  469. 

Eider,  347. 

Elasmobranchii,  279. 

Eiassoma,  271. 

Elk,  *394,  396. 

Epeiridoe,  236. 

Ephemeiida,  194. 

Epialtus  productits,  *  1 53 . 

Equipment  of  laboratory,  450. 

Equipment  of  pupil,  447. 

Erethizon  dorsatus,  391. 

Erethizon  epixanthus,  391. 

Eretmochelys  imbricata,  215. 

Erismatura  rubida,  347. 

Eiimeces  skeltonianus,  *3i6. 

Eitpomotic  gibbosuc,  dissection  of, 
(facing)  *263;  life  of,  270  ;  struc- 
ture of,  263. 

Exoccetus,  285. 

Eye,  cornea  of  compound,  of  horse, 
fly,   *i86  ;  section   throiu  ' 
pound,  of  blow-fly,  *i 

J^y0  of  vertebrate,  *378. 

Ealco  sparverius,  353. 
Kami'lv.   rlpfinpfl.   Tz. 


INDEX 


477 


Fauna,  440. 

P'eather-stars,  1 21,  125,  *I26. 

Feet  of  birds,  362. 

Felis  concolort  398. 

Ferae,  397. 

Fever,  yellow,  and  mosquitoes,  205. 

Fiber  zibet  hi  cus,  391. 

Fire-flies,  209. 

J  ishes,  263;  body  form  and  struc- 
ture of,  271;  classification  of,  277; 
development  and  life-history  of, 
276;  habits  and  adaptations  ci, 
285. 

Fish-hatcheries,  288. 

Flat-worms,  137. 

Flea,  house,  *2O4. 

Flickers,  355. 

Flies.  201 ;  chalcid,  214;  ichneumon, 

212. 

Flight  of  birds,  366. 

Flying  fishes,  285. 

Food- fishes,  288. 

Food  of  birds,  370. 

Foraminifera,  80. 

Fox,  398. 

Fregata  aquila,  346. 

Frogs,  299. 

Fulica  americana,  349. 

Fulmars,  345. 

Function,  defined,  14. 

Functions,  essential.  15. 

Fur-seals,  398,  *399- 

Fur-seals,  parasitized,  *422. 

Gadus  callnrias,  284. 

Galley-worm,  *227- 

Gall-flies,  214. 

Gallinae,  350. 

Gastropoda,  246. 

Gavia  imber,  347. 

Gavial,  326. 

Generation,  spontaneous,  58. 

Genmules,  85. 

Genus,  defined.  70. 

Geococcvx  calijornianns,  354. 

Gephyrean,  *I34- 

Girdler,  currant  stem,  *2I5. 

Glass-snake,  317. 

G I  ires,  391. 

Goat.  Rocky  Mt.,  397. 

Gonionema  vert  ens.  *ioi. 

Goose,  Canada,  347. 

Gophers,  pocket,  391. 

Gordius,  140. 

Granlia,  *47- 


:    Grunt ia  sp.,  85. 

I   Grayling.  284, 

:  Grebe,      horned,     343;     pied-billed, 

343- 

i  Green,  methyl,  351. 
Greensnake,  320. 
Gregariousness,  410. 
Grouse,  ruffed,  350. 
Grus  americana,  348. 
Grits  mexicana,  348. 
Guillemot,  345. 
Guinea-pig,  391. 
Guinea -worm,  140. 
Gull,  great  black  backed,  345. 
Gulls.  345. 
Gymnophiona,  302. 
Gyrinidge,  206. 

Habitat,  441. 

Hag-fishes,  279. 

Hair-worms,  140. 

Hal'uctus  leucocephalus,  352. 

Ha  lie  tits,  216. 

Harporhvnchus  redivh'iis^  *37i. 

Hatteria.  312. 

Hawk,  marsh,  352. 

Helmet  shells,  255. 

H.loderma  horridum.  ^317. 

Hemiptera,  197. 

Hermit-crab,  154.  *I53- 

Herodiones,  347. 

Htron,  great  blue,  348  ;  green.  347. 

Herring,  284. 

Heteredon  pla  tirh  inos,  321. 

Hippocampus  hippocampus,  *285- 

Holothuroidea,  12 1,  124. 

Honto  sapiens \  398. 

Honey-bee,  *2i8  ;  brood-cells  of. 
*2I9;  building  comb,  *22l;  comb 
of  East  Indian,  *222;  cross-sec- 
tion of  body  of  pupa  of,  *igi. 

Honey-bees.  212. 

Honey-dew,  food  of  ants,  223. 

Hornets,  217. 

Horse-fly,  cornea  of  eye  of,  *i86 

House-fly.  202. 

Humming-birds.  356. 

Hydra.  ^47;  structure  and  life  of,  46. 

HydraoEoa,  96,  97. 

Hydrophilidae,  207. 

Hydrophilus  sp..  external  structure 
of,  *i64 ;  internal  structure  of, 


Ilygrotrechus,  198,  *I99- 
Hyia  pickeringii,  300. 


478 


INDEX 


Hyla  versicolor,  300. 
Hymenoptera,  212. 
Hyptiotes  sp.,  and  web,  -238. 

Iguana,  318. 

Imago,  190. 

Injecting-masses,  451. 

Insect,  pinned,  *465;  twig,  *42j; 
wingless,  *i8i. 

Insecta,  157. 

Insectivora,  391. 

Insects,  classification  of,  191;  col- 
lecting, 463;  communal,  215;  de- 
velopment and  life-  history  of,  188; 
form  and  structure  of,  181  ;  killing- 
bottle  for,  *463;  social,  215. 

Invertebrate,  defined,  30. 

Islands,  coral,  104,  106. 

Isopod,  *I5I. 

Isopoda,  150. 

Jack  rabbit,  390. 
Janus  integer,  *2I$. 
Jellyfish,  *ioi. 
Jelly  fishes,  92;  colonial,  97. 
Joint-snake,  318. 
Jit  Ins,  ^327. 
June-beetle,  212. 
June-beetles,  206. 


Kallima, 

Kangaroo,  389. 

Katydids,  192. 

Kelp-crab,  *I52. 

Kill-deer,  349. 

Killing-bottle  for  insects,  *463- 

Kingfisher,  belted,  354. 

Laboratory,  equipment  of,  450. 
Lachnosterna,  212. 
Lady-birds,  209. 
Lagopus,  350. 
Lake-lamprey,  279. 
Lampetra  wilderi,  279. 
Lamprey,  *278;  brook,  279. 
Lampropeltis  boy  Hi*  *32l. 
Lampropellis  getulus,  320. 
Lancelet,  278. 
Larks,  horned,  *358. 
Larus  marinus,  345. 
Larva,    189;    of   Monarch  butterfly, 
anatomy     of,      177  ;     parasitized. 

*420. 

Lasiiirus  borealis,  392. 
Lasiurits  cinereus. 


Lasius  flttvuS)  223. 

Leeches,  136. 

Lemurs,  401. 

Leitcania  unipuncta,  *2ii. 

Lepidocyrtus  americanus,  *i8i. 

Lepidoptera,  205. 

Leptocardii,  277. 

Leploplana  calif  arnica,  *I38. 

Lepus  campestris,  390. 

Lepus  mtttali,  390. 

Life-history,  defined,  62. 

Life-processes,  essential,  15. 

Limicolse,  349. 

Limpets,  255,  *248. 

Littorina  scutulata,  *248. 

Live  cages,  457. 

Liver  of  toad,  structure  of,  41. 

Lizard,  *3O9. 

Lizards,  316. 

Lobster,  151,  152. 

Locust,  differentia],  156  ;  ear  of. 
*i87  ;  red-legged,  156,  *I57; 
Rocky  Mt.,  156;  structure  and  liie 
of,  156;  two- striped,  156. 

Locusts,  192. 

Loligo,  257. 

Longipennes.  345. 

Loon,  343. 

Lttmbricus  sp.,  alimentary  canal  of, 
*  13 1;  cross-section  of,  *I32;  struc- 
ture and  life  of,  127. 

Lung-fish,  285. 

Lycena ,  scales  of  wings  of,  *2o6. 

Lycosidre,  235. 

Lynx  rufus,  398. 

Macrocheira.  154. 

Madrepora  cervicornis,  *IO5- 

Malaclemmys  palustris,  3 1 4. 

Malaria  and  mosquitoes,  105. 

Mallard,  347. 

Mammal,  circulation  of  blood  in. 
*376. 

Mammalia,  373. 

Mammals,  373  ;  body  form  and 
structure  of,  381;  classfl||ation  of, 
389;  development  and  Imkhistory 
of,  388;  habits,  instinct  anxr* rea- 
son of,  388  ;  making  skins  of, 
470. 

Man,  398. 

Man-of-war,  Portuguese,  98,  *97. 

Marsupialia,  389. 

Martesia  xylopkaga,  *2$i. 


INDEX 


479 


May- flies,  194. 

May-fly,  nymph  of,  *IQ7. 

Medusa.  *ioi. 

Megalobatrachus,  298. 

Mc-gascops  asio.  *352,  353. 

Mt-lancrpt's  t-rythrocephalus,  355. 

Melanerpes  fonnicivonis,  356. 

Melanoplus  sp.,  ear  of,  *i8j;  struc- 
ture and  life-history  of,  157. 

Jlfe/anoplus  vibiftatns,  157* 

Mc'lanoplns  differentialis,  157. 

Melanoplns  femur-  rubrum,  1 5  7 .  *  1 5  8. 

Melanoplns  spretns,  157. 

Mcleagrina  margaritifera,  250. 

ML  -rn  la  mi gr  atari  a  propinqua.  *368. 

Metamorphosis,  complete,  I71?  188, 
189;  incomplete,  171,  189. 

Metazoa,  defined,  43. 

Mice,  391. 

Micropleriis  dolomien,  282. 

MicroptiTus  salmoides,  282. 

Migration  of  birds,  367. 

Mimicrv,  430. 

Millipeds,  226. 

Mite,  cheese,  *23O. 

Mites,  229. 

Modifications  of  structure  and  func- 
tion, 29. 

Moles,  391. 

Mollusca,  239. 

Molluscs,  239;  classification  of,  246; 
development  of,  246 ;  form  and 
structure  of,  245. 

Molting,  361;  of  birds,  361. 

Monitor,  318. 

Monkey,   *4OO. 

Momomeriiun  minutiitn,  *22\. 

Monster,  Gila,  *3I7- 

Moose,  *385,  396. 

Morphology,  defined,  3. 

Mosquito,  202,  *2O3. 

Mosquitoes,  201;  and  malaria,  205  ; 
and  yellow  fever,  205. 

Moth,  forest  tent-caterpillar,  life- 
history  of,  *2C»7. 

Moths,  205. 

Mourning  dove,  351. 

Mouse,  life-history  and  habits  of, 
379;  structure  of,  373. 

Mud-eel,  297. 

Mud-hen,  349- 

Mud-puppies,  297. 

Mud-turtle.  313. 

Multiplication  of  one-celled  animals. 
59;  of  many- celled  animals,  61. 


Murres.  *344- 

Muscles  of  toad,  structure  of,  41. 
^flls  deciimanus,  391. 
Mus  Diiisculus,  structure  of,  373. 
Mus  rat  tits,  391. 
Musk-rat,  391. 

Mussel,  fresh-water,  life-history  and 
habits     of,     243;      structure     of, 

239- 

Mya  arenaria,  247. 
Afyotis  siibiilatus,  392. 
Myriapoda.  144,  226. 
Mytilus  californiamts,  *248. 
Myxiitc,  279. 

Names,  scientific,  68. 
Xarcobatis,  281. 
\atrix  sipedon,  320. 
Nautilus,  255;  pearly.  258. 
Xantilus  pompilhis,  258. 
Necturus.  297.  298. 
Nemathelminthes,  140. 
Neotoma  pennsylvanica,  391. 
Nereid,  *I34- 
Nereis  sp.,  *I34. 
Nesting  of  birds,  366. 
Nest  of  oriole.  *365. 
Nettion  carolinense,  347-] 
Night-hawk,  356. 
Night-heron,  348. 
Nirnnts  prastans,  *  194. ' 
Non-calcarea,  91. 
Notes,  447,  448. 
Notochord,  259. 
Notonecta,  197,  199. 
Nucleus,  38. 

Nudibranchs,  252,  *254. 
A'nmenius.  longirostris,  350. 
Nyctea  nyctea,  353. 
Nycticorax,  348. 

Octopi,  255. 

Octopods,  256. 

Odocoileus  americanus,  396. 

Odonata.  194. 

Oligochaetae,  136. 

Olor,  347. 

Ominatostrephes  californifa.  *2tfl. 

Oncorhynchus  tschawtsc/m,  283. 

One-celled     animals,    multiplication 

of,  57- 
Ooze,    foraminifera,  81  ;  radiolaria, 

81. 
Opheosaurtis  vcntralis,  317. 


480 


INDEX 


Ophiuroidea,  121,  122. 

Opossum,  389. 

Order,  defined,  72. 

Oreamnos  montanus,  397. 

Organ,  defined,  14. 

Orthoptera,  192  ;  sound-making    of, 

193- 

Orb- web  of  Epeiridae,  236. 
Ostrea  virginiana,  248. 
Ostriches,  341,  *342. 
Otocoris  alpestris,  *358. 
Ch'is  canadensis,  *Z&Z,  39^- 
Owl,    burrowing,    353;  great   gray, 

353  ;  great   homed,  353  ;  snowy, 

353- 

Oyster,  248. 
Oyster-crab,  154. 
Oyster-drills,  255. 
Oysters,     246;      "seed"    of,     249; 

"  spat  "  of,  249. 

Pagunts  saninelis,  *I53- 

Paludicolae,  348- 

Panther,  398. 

Paramcedum ,  '"'35;  multiplication  of, 
60;  structure  and  life  of,  34. 

Parasitism,  415. 

Paroquet,  Carolina,  353. 

Parrots.  353. 

Passer  domestictts,  dissection  of,  (fac- 
ing) ^327  ;  life-history  and  habits 
°f»  335:  structure  of,  327. 

Passeres,  357. 

Pearl-oyster,  *249. 

Pelecanus  californicus,  346. 

J^elecanus  ervthrorJiynchns,  346. 

Pelecanus fuscHS i  346. 

Pelecypoda,  246. 

Pelican,  brown,  346;  white,  346. 

Pentacrimis  sp.,  *I26. 

Peutacta  frondosa.  *I25. 

Peri  pat  us  eiseni,  *226. 

Perla  sp.,  *i82. 

Petrels,  345. 

Petroniyzon  inarinus ,  *278. 

/  halacro corax,  346. 

Pheasants,  350. 

Phoca  vitulina,  397. 

Phoebe,  black,  nest  and  eggs  of, 
*340. 

Pholas  sp.,  ^250. 

PJnynosotna,  318. 

Phylloxera,  grape,  198,  201. 

Phvlloxera  vastatrix,  198,  201. 

Phylum,  defined,  73. 


Physalia  sp.,  *97. 

Physetcr  macrocephalus,  393. 

Physiology,  defined,  3. 

Pici,  354. 

Pickerel-frog,  300. 

Pigeon,  band-tailed,  351;  passenger, 

351- 

Pinnotheres,  154. 

Pipe-fish,  285. 

Pisces,  263. 

Pituophis  bellona.  *323. 

Planar ia  sp.,  *I38. 

Planarian,    fresh-water,    *I38  ;  ma- 
rine, *I38. 

Planarians,  137. 

Plant-lice.  197,  200. 

Planula,  96. 

Platyhelminthes,  137. 

Plectrophenax  nil*  a  Us,  *358. 

Plethodon,  297. 

Plover,  field,  349. 

Pluteus,  119. 

Podilymbus  podiceps,  343. 

Poison-fangs  of  rattlesnake,  *324. 

Pollicipes  poly  menus,  *  1 5  3 . 

Polymorphism,  96. 

Polynce  brevisetosa,  *I34- 

Polyps,  92,  97. 

Pomoxis  annularis,  282. 

Potnoxis  separoides,  282. 

Pond-snails,  252. 

Porcupine,  390. 

Porcupine-fish,  285. 

Porifera,  84. 

Porpoises,  393. 

Porzana  Carolina,  349. 

Prairie-chicken.  350. 

Prawns,  152. 

Preparations,  preserving  anatomical, 

452- 

Primates,  398. 

Pristis  pectinatis,  281. 

Protophyta,  82. 

Protoplasm,  described,  39. 

Protopterus,  288. 

Protozoa,    defined,  43,  75;  form    of, 

78;  marine,  80. 
Pseudemys,  313. 

Pseudogryphus  californianns,  352. 
Psittaci,  353. 
Ptarmigan,  356. 
Puff-adder,  325. 
Puffins,  345. 
JUlex  irritans,  *2C4 
Pulmonata,  25^, 


INDEX 


481 


Puma.  398. 

Pumpkin  seed,  life  of,  270;  structure 

of,  263. 
Pupa,  189;  cross-section  of  body  of, 

of  honey  -bee,  *I91. 
Pupation,  189. 
Pnrpura  saxicola^  *248. 
Pygopodes,  343. 
Python,  324. 

Quail,  350. 

Qiierqiieditla  discors,  347. 

Rabbits,  390. 

Radiolaria,  80. 

Rai',  Carolina,  349. 

Raja  erinacea,  280,  *28l. 

Raja  liei'is,  281. 

Rana  catesbiana,  299. 

Rana  palustris,  300. 

Rana  sylratica,  300. 

Rangifer  caribou,  396. 

Raptores,  351. 

Ratitae,  341. 

Rats.  391. 

Rattlesnake  poison-fangs,  *324. 

Rattlesnakes,  321. 

Rattles  of  rattlesnake,  *223. 

Reefs,  coral.  106. 

Reindeer,  396. 

Remora,  ^87. 

Remoropsis  brachyptera,  *287- 

Root-cage,  460. 

Reptiles,  body  form  and  organiza- 
tion of,  309;  classification  of,  312; 
life-history  of,  312;  structure  of, 
310. 

Keptilia,  303. 

Resemblance,  protective,  326. 

Rheas,  343. 

Road-runner,  354. 

Robber -ant,  225. 

Robin,  Western,  *368. 

R(x;k-bass,  282. 

Rock-crab,  *I53. 

Rock-dove,  351. 

Rodents,  390. 

Rosalina  variant,  *8i. 

Rotifer  sp.,  *I43- 

Round  worms,  140. 

Ruminants,  395. 

Sacculina,  67,  *4i8. 
Sage-hen,  350. 

Salamander,  red-backed,  297 ;  tiger, 
'292. 


Salamanders,  297. 

Salmo  irideits,  *28j. 

Salmon,  king.  284. 

Sand-dollar,   124. 

Sand  -pipers,  345. 

Sanninoidea  exist  iosa,  *2I2. 

Sap-  sucker,  downy,  355;  hairy,  355, 

Saw-fish,  281. 

Sayornis    nigricans,  nest   and    eggs 

of,  *340. 

Scale  insect,  red-orange,  *I98. 
Scale  insects,  198. 
Scale  rose,  ^198. 
Scales  of  wings  of  Lyccena,   *2o6  ; 

wing  of  Monarch  butterfly,  *I74- 
Scallops,  246. 
Scalops  aquaticus,  391. 
Scaphiopiis,  300. 
Sceloporus,  317. 
Sciuropterus  rolans,  391. 
Sciurus  carolinensis,  391. 
Sciurus  httdsonicus,  391. 
Sciurus  ludovicianus,  391. 
Scolopendra  sp.,  228,  229. 
Scorpion,  *23O. 
Scorpions,  229. 
Scoliaptex  cinera,  353. 
Screech-owl,  *352,  353 
Scutigera  Jorceps,  *228. 
Scyphozoa,  97,  101. 
Sea  anemones^  92,  102,  *IO3. 
Sea  cucumljer,  *I25. 
Sea-cucumbers,  108,  121, 
Sea-fan.  107. 
Sea-feather,  106. 
Sea-horse,  *285. 
Sea-lamprey,  279. 
Sea-lily,  118. 
Sea-pen,  106. 
Sea-shells,  252. 
Sea-slugs,  255. 
Sea-snakes,  325. 
Sea-squirt,  *26i. 
Sea-turtles,  315. 

Sea-urchin,  *H4;  structure  of,  113. 
Sea-urchins.  JOS^  121,  123. 
Seals,  397. 
Selection,    artificial,    409  ;     natural, 

406. 

Sembling  of  insects,  176. 
Sepias,  256. 
Setting-board    for    butterflies,    ^466, 

467. 
Shark,  basking,   270,  280;   hammer- 

headed,  280;  man-eating,  280, 


124. 


482 


INDEX 


Sharks,  280. 

Shearwaters.  345. 

Sheep-fluke,  138. 

Sheep,  Rocky  Mt.,  *383,  397. 

Ship  worm,  251. 

Shoveller,  347. 

Shrews,  391. 

Shrimp,  151,  152. 

Silk-worm,  anatomy  of,  *I78. 

Siphonophore,  98. 

Siren,  297,  298. 

Sistrurus,  322. 

Skate,  barn-door,  281;  common,  280, 

*28l. 

Skates,  280. 
Skeleton  of  coral,  105. 
Skeletons,  preparing,  452. 
Skink,'blue  tailed,  #317. 
Skin  of  toad,  structure  of,  40. 
Slipper-animalcule,    *35  ;    structure 

and  life  of,  34. 
Slug,  giant  yellow,  ^252. 
Slugs,  252,  253. 
Snake  coral,  321. 
Snake,    garter,    *32o;   life   of,  307; 

structure  of,  303;  gopher,  ^322. 
Snake  king,  *32i. 
Snakes,  316. 
Snails,  252,  253. 
Snapping-turtle,  314. 
Snipes,  349. 
Snowflakes,  *358. 
Snow-goose,  347. 
Social  life.  410. 
Somateridi  347. 
Songs  of  birds.  364. 
Sora,  349. 

Sound  making  of  orthoptera,  193. 
Spadefoot,  300. 
Sparrow,      English,     dissection     of, 

(facing),    *327  ;    life-history    and 

habits  of,  335;  structure   of,   327; 

western  chipping,  *36o. 
Sparrow-hawk,  353. 
Spatula  clypeata,  347. 
Species,  defined,  69, 
Species-extinguishing,  442. 
Species-forming,  408,  442. 
Speotyto  cunicularia,  353. 
Sphinx  t'/iersis  larva,  *43i. 
Sphinx-moth,     pen-marked,     larva, 

*43L 

Sphyma,  280. 
Spicules,  sponge.  85. 
Spider  and  web,  *237. 


Spider,  crab,  '-235;  jumping.   ^235 
long-legged,  *233;  running,  *234. 
running  with  egg-sac,   *234;    tri- 
angle, and  web,  *238. 

Spider-crab,  154. 

Spiders,  229;  hunting,  233;  seden- 
tary, 233;  trap-door,  233;  wander- 
ing, 233;  wtb  weaving,  233. 

Spinnerets  of  spider,  *233. 

Spizella  soda  Us  arizomc,  *36o. 

Sponge,  commercial,  86  ;  fresh- 
water, 84;  glass,  *87;  skeleton  of. 
88 ;  structure  of.  88. 

Sponges,  84;  calcareous  ocean,  8t,; 
classification  of,  91;  development 
and  life-history  of,  89  ;  feeding 
habits  of,  88  ;  form  and  size  ol. 
87;  of  commerce,  90. 

Spongin,  86. 

Spongilla  sp.,  84. 

Springtail,  American,  *i8i. 

Squamata,  312.  316. 

Squid,  great,  *257. 

Squids,^255,  257. 

Squirrels,  391. 

Starfish,  *KK);  cross-section  of.  *H2. 

&tarfishes,~io8,  121. 

Stentor  sp.,  *79- 

Sterna,  345. 

Sterna  maxima,  194. 

Sting-ray,  281. 

Stone- fly,  *i82. 

Strix  pratincola,  353. 

Strongylocentrotus  sp.,  structure  of, 

"3- 

Strongvlocentrotiis  fr  a  n  c  i  s  c  a  n  it  s. 
*H5,  122;  structure  of,  115. 

Struggle  for  existence,  406. 

Strut hio  came/us,  342. 

Sub-species,  69. 

Suckers,  283. 

Sucking-bugs,  197. 

Sun  animalcule,  *78. 

Sunfish,  dwarf,  271;  golden,  dissec- 
tion of,  (facing)  *2&3;  life  of,  270; 
structure  of,  263. 

Supplies,  obtaining  laboratory,  453. 

Swans,  347. 

Swarming  of  honey-bee,  219,. 

Swell-fish,  285. 

Swift,  common,  316. 

Sword-fish,  285. 

Symbiosis,  155,  413. 

Symmetry,  bilateral,  5 ;  radial,  108. 

Sy  nip  drum  illoiuin,  *I96. 


INDEX 


Syngnathns  fuscHtti.  285. 


Tadpole,  55. 

Tadpoles,  *2g6. 

Tania  solium,  139. 

Tapeworm,  139. 

Teal,     blue  winged,     347  ;     green- 

winged,  347. 
Teleostomi,  282. 
Tell-tale,  349. 
Teredo,  251. 
Tern,  194. 
Terns,  345. 
Terrapin,    diamond  -back,  314;  red- 

bellied,  314;  yellow-bellied,  314. 
Testudo  sp.,  *3I5- 
Tetragnatha  sp.,  *233- 
Thalarctos  maritimus.  398. 
Thamnophis  sp.,  life  of,  307;  struc- 

ture of,  303. 

Thamnophis  parietalis,  *32O. 
Theridiae,  235. 
Therioplectes    sp.,    cornea    of   com- 

pound eye  of,  *i86. 
Thomisidae,  235. 
Thrasher,  sickle-billed,  *3;i. 
Tlirush,  russet  backed,  *363. 
Thvmallus  signifer,  284. 
Ticks,  229. 
Tiger-beetles,  209. 
Toad,   cellular  structure  of,  40;  de- 

velopment of,  55  ;  garden,   dissec- 

tion of,  5;  horned,  317  ;  skeleton 

of,  *n. 

Toads,  299,  300. 
Torpedo,  281. 

Tortoise,  Galapagos  giant,  *3i5- 
Tortoises,  313. 
Tortoise-shell,  315. 
Totamis  melanoleucus,  349. 
Trachea,  *i84- 
Tree-frogs,  300. 
Tree-toads,  300. 
Trepang,  124. 
Trichina,  140. 
Trichina  spiralis,  141.  *i4i. 
Trichinosis,  141. 
Triopha  modesta,  *254. 
Tripoli  rock,  82. 
Triton,  green.  297. 
Trochilus    colubris,    356  ;    nest   and 

eggs  of,  *357. 
Trout,  rainbow, 
Tumble  bugs,  209. 
Turdus  ustutains, 


Turkeys,  wild,  350. 

Turtle,  green,  315  ;  hawk-bill,  315  ; 

logger-head.  315. 
Turtle-dove,  351. 
Turtles,  313. 

Tympamichus  americanus^  350. 
Tyroglyphus  siro,  *2T>o. 

Ungulata,  393. 

L'nio  sp.,  life-history  and  habits  of, 

243;  structure  of,  239. 
L~ria  troile  calif ornica,  *344- 
Ursus  americamiSj  398. 
Ursns  horribilis,  398. 

Varanns  niloiicits,  318. 

Variation,  406. 

Variety,  69. 

Venation  of  wings  of  insects.  174;  of 
wings  of  Monarch  butterfly.  *I75- 

Vemts  mercenaria,  247. 

Verities,  127;  life-history  and  hab- 
its of,  132;  classification  of,  135. 

Vertebrate,  defined,  30;  brains  of, 
376;  eye  of,  *379. 

Vertebrates,  259;  structure  of,  259. 

Vespidse,  217. 

Vinegar-eel,  140,  *I4O. 

Viper,  324;  blowing,  321. 

Viper  a  cerasta,  324. 

Vorticella  sp.,  *"j6. 

Vorticella,  structure  and  life  of,  75. 

Vttlpes  pennsylvanicus,  398. 

Walking-stick,  193,  194. 
Wapiti,  *394- 

Wasps, 2 12;  digger,2!7;  solitary,2i7. 
Water-beetle,  predaceous,  210. 
Water-beetles,  206. 
Water-boatman,  *I99. 
Water-boatmen,  197. 
Water-flea,  148,  *H9. 
Water-dog,  298. 
Water-snake.  320. 
Water-strider,  197,  199,  *I99. 
Water  tiger,  212,  *2I4. 
Weevils,  209. 
Whalebone,  393. 
Whales,  393. 
Wheel-animalcule,  *I43. 
Whip-poor-will,  356. 
Whitefish,  284. 
Wild -cat,  398. 

Wings  of  Monarch  butterfly  showing 
venation,  *I75- 


484 


INDEX 


Wolf,  398. 

Woodchuck,  391. 

Wood-duck,  347. 

Wood-frog.  300. 

Wood-lice,  150. 

Woodpecker,  California,  356;  ivory- 
billed.  355;  red-headed,  355. 

Woodpeckers,  354. 

Wood-rat,  391. 

Worm,  army,  *2II. 

Worms,  127;  life-history  and  habits 
of,  133;  classification  of,  135;  ma- 
rine, *I34- 


Xiphias  gladius,  285. 

Yellow-hammer,  *355. 
Yellow-jackets,  217. 
Yellow- shank,  349. 

Zenaidura  macroura,  351. 

Zoogeography,  436. 

Zooids,  98. 

Zoology,  a  first  course  in,  3;  de 
fined,  3;  divisions  of,  2;  system- 
atic, defined,  3. 

Zoophytes,  92. 


MAR  is  m 

8  ^921  S''    *    v^JWI 


DEC  1 0  1940 


65488 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


